Capsule-type endoscope

ABSTRACT

A capsule-type endoscope includes a capsule, an objective optical system, an image pickup element, and at least one illumination light source having a light-emitting surface, and a transparent cover. In several embodiments of the capsule-type endoscope according to the present invention, an inner surface of the transparent cover is spherical within a field of view of the objective optical system so as to have a center of curvature, the center of curvature is offset from the optical axis of the objective optical system, and a specified condition is satisfied so as to avoid flare in the objective optical system caused when light from the one (or more) illumination light source(s) enters the entrance pupil of the objective optical system. In another embodiment, the inner surface of the transparent cover has the shape of an ellipsoid. Observation methods using the capsule-type endoscope are also disclosed.

This application claims the benefit under 35 U.S.C. § 119 of JP2004-228170, filed Aug. 4, 2004, the contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

Conventional capsule-type endoscopes contain, for example, an objectiveoptical system, an illumination means, an image pickup element, and atransmission means within a capsule-shaped shell. A cover member(hereinafter termed a transparent cover) that is generally spherical inshape and transparent within the field of view of the objective opticalsystem seals these items within the capsule-shaped shell. Typically, acapsule-type endoscope having the above-discussed structure convertsinto signals in vivo images that are captured on a light-receivingsurface of the image pickup element. These signals, of images that havebeen captured using light that has passed through the transparent coverand the objective optical system, are then transmitted externally bymeans of the transmission means. The transmitted signals are received byan external receiver device, and are then displayed on a display devicefor examination.

Capsule-type endoscopes as discussed above have a problem in thatillumination light emitted from the illumination means is partlyreflected by the inner surface of the spherical transparent cover andenters the entrance pupil of the objective optical system, which causesflare and significantly deteriorates the image contrast.

The inventions as disclosed, for example, in the following prior artpatent documents have been proposed to prevent light that is reflectedby the inner surface of the transparent cover from reaching the entrancepupil of the objective optical system and causing flare.

Japanese Laid-Open Patent Application 2003-325441 discloses acapsule-type endoscope in which the transparent cover has a sphericalinner surface and the center of the entrance pupil of the objectiveoptical system coincides with the center of curvature of this surface.Light that is emitted from the illumination means and reflected by theinner surface of the transparent cover is prevented from reaching theentrance pupil of the objective optical system, thus preventing flare.Also, Japanese Laid-Open Patent Publication 2003-501704 discloses anoptical device in which the transparent cover has an ellipsoidal innersurface and multiple light sources that function as an illuminationmeans are provided along a focal curve on the focal plane of theellipsoid. Once again, the light that is emitted from the illuminationmeans and reflected by the inner surface of the transparent cover isprevented from reaching the objective optical system and causing flare.

However, the capsule-type endoscope disclosed in Japanese Laid-OpenPatent Application 2003-325441 requires that the illumination means bepositioned around the objective optical system because of the structurethat the center of the entrance pupil of the objective optical systemcoincides with the center of curvature of the inner surface of thetransparent cover. This disadvantageously increases the size of thecapsule-type endoscope.

As noted above, the light emitting elements that are used as theillumination means of the optical device disclosed in Japanese Laid-OpenPatent Publication 2003-501704 must be located on the focal curve.Consequently, in order to provide sufficient room in which to mountthese light- emitting elements, the transparent cover has to beincreased in size, which requires that the size of the capsule-typeendoscope itself be larger.

Furthermore, it is desired that the capsule-type endoscope describedabove provide a space for carrying a battery for ensuring sufficientoperation time of the capsule-type endoscope or a tank for carrying asubstance in liquid form. However, when an attempt is made to providesuch a space in the prior art capsule-type endoscopes discussed above,the location of such a space must be such that no interference occursbetween the objective optical system and the illumination means. Thisrequirement tends to increase the size of the capsule-type endoscope.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a capsule-type endoscope that can beswallowed for an in vivo examination. The purpose of the presentinvention is to provide a capsule-type endoscope that can prevent lightthat is reflected by the inner surface of the transparent cover fromcausing flare in the objective optical system, even if the size of thecapsule-type endoscope is decreased.

Another purpose of the present invention is to provide a capsule-typeendoscope that can prevent light that is reflected by the inner surfaceof the transparent cover from causing flare in the objective opticalsystem while simultaneously providing a sufficient space for mountingeither a tank for carrying a substance in liquid form (such as acoloring agent or drug) for applying to a target region of a patient ora battery for increasing the operating time of the capsule-typeendoscope.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given below and the accompanying drawings, whichare given by way of illustration only and thus are not limitative of thepresent invention, wherein:

FIGS. 1(a) and 1(b) are cross-sections of a front portion of acapsule-type endoscope as viewed from the side and front, respectively;

FIG. 2 is a cross-section of a front portion of a capsule-type endoscopeas viewed from the side that shows forming images of object pointslocated on the outer surface of the transparent cover at the outerlimits of the field of view of the objective optical system;

FIGS. 3(a) and 3(b) are illustrations which relate to Embodiment 1 ofthe present invention, with FIG. 3(a) being a cross-section of a frontportion of the capsule-type endoscope as viewed from the side, and FIG.3(b) being a cross-section of the front portion of the capsule-typeendoscope as viewed from the front;

FIGS. 4(a) and 4(b) relate to a first possible modification toEmbodiment 1 of the present invention, with FIG. 4(a) being across-section of a front portion of the capsule-type endoscope as viewedfrom the side, and FIG. 4(b) being a cross-section of a front portion ofthe capsule-type endoscope as viewed from the front;

FIGS. 5(a) and 5(b) relate to a second possible modification toEmbodiment I of the present invention, with FIG. 5(a) being across-section of a front portion of the capsule-type endoscope as viewedfrom the side, and FIG. 5(b) being a cross-section of a front portion ofthe capsule-type endoscope as viewed from the front;

FIG. 6 shows the positional relationships of the field of view of theobjective optical system of a capsule-type endoscope, a jet orifice of anozzle for spraying a substance in liquid form onto a target region, andthe observation target region of the capsule-type endoscope according tothe second possible modification to Embodiment 1 shown in FIGS. 5(a) and5(b);

FIG. 7 shows an embodiment of the capsule-type endoscope in which thejet orifice of a nozzle is positioned within the field of view of theobjective optical system;

FIG. 8 shows an exemplary structure of a capsule-type endoscope that isprovided with a delivery tube having a puncture needle at one end of thedelivery tube;

FIG. 9 shows another exemplary structure of a nozzle, as well as of apuncture needle projection port, with the capsule being shown incross-section as viewed from the side;

FIG. 10 is an illustration to explain the capsule-type endoscope systemof the present invention that may be used to observe the inner wall of aperson's digestive tract;

FIGS. 11(a) and 11(b) illustrate Embodiment 2 of the present invention,with FIG. 11(a) being a cross-section of a front portion of thecapsule-type endoscope as viewed from the side, and FIG. 11(b) being across-section of a front portion of the capsule-type endoscope as viewedfrom the front;

FIGS. 12(a) and 12(b) illustrate a first possible modification toEmbodiment 2 of the present invention, with FIG. 12(a) being across-section of a front portion of the capsule-type endoscope as viewedfrom the side, and FIG. 12(b) being a cross-section of a front portionof the capsule-type endoscope as viewed from the front;

FIGS. 13(a) and 13(b) illustrate a second possible modification toEmbodiment 2 of the present invention, with FIG. 13(a) being across-section of a front portion of the capsule-type endoscope as viewedfrom the side, and FIG. 13(b) being a cross-section of a front portionof the capsule-type endoscope as viewed from the front;

FIGS. 14(a) and 14(b) illustrate a third possible modification toEmbodiment 2 of the present invention, with FIG. 14(a) being across-section of a front portion of the capsule-type endoscope as viewedfrom the side, and FIG. 14(b) being a cross-section of a front portionof the capsule-type endoscope as viewed from the front;

FIGS. 15(a) and 15(b) are illustrations to show exemplary structure of acapsule-type endoscope according to the present invention so as toclarify the differences between the present invention versus prior artcapsule-type endoscopes, with FIG. 15(a) being a cross-section of afront portion of a capsule-type endoscope according to the presentinvention as viewed from the side, and FIG. 15(b) being a cross-sectionof a front portion of a capsule-type endoscope according to the presentinvention as viewed from the front;

FIGS. 16(a) and 16(b) show another exemplary structure of a capsule-typeendoscope according to the present invention so as to clarify thedifferences between the present invention versus prior art capsule-typeendoscopes, with FIG. 16(a) being a cross-section of a front portion ofa capsule-type endoscope according to the present invention as viewedfrom the side, and FIG. 16(b) being a cross-section of a front portionof a capsule-type endoscope according to the present invention as viewedfrom the front;

FIG. 17 relates to Embodiment 3 of the present invention, andillustrates the imaging of object points that are on the outer surfaceof the transparent cover at the outer limits of the field of view of theobjective optical system;

FIG. 18 relates to Embodiment 4 of the present invention, andillustrates the imaging of object points that are on the outer surfaceof the transparent cover at the outer limits of the field of view of theobjective optical system;

FIGS. 19(a) and 19(b) relate to Embodiment 5 of the present invention,with FIG. 19(a) being a cross-section of a front portion of thecapsule-type endoscope as viewed from the side, and FIG. 19(b) being across-section of a front portion of the capsule-type endoscope as viewedfrom the front;

FIGS. 20(a) and 20(b) relate to Embodiment 6 of the present invention,with FIG. 20(a) being a cross-section of a front portion of thecapsule-type endoscope as viewed from the side, and FIG. 20(b) being across-section of a front portion of the capsule-type endoscope as viewedfrom the front;

FIGS. 21(a) and 21(b) relate to Embodiment 7 of the present invention,with FIG. 21(a) being a cross-section of a front portion of thecapsule-type endoscope as viewed from the side, and FIG. 21(b) being across-section of a front portion of the capsule-type endoscope as viewedfrom the front;

FIGS. 22(a) and 22(b) show a capsule-type endoscope in which a nozzleand tank for carrying a substance in liquid form are constituted as aunit that is detachably attached to the capsule-type endoscope;

FIGS. 23(a) and 23(b) show a capsule-type endoscope in which a punctureneedle projection port, a puncture needle storage part, and a mechanismfor pushing out the puncture needle are constituted as a unit that isdetachably attached to the capsule-type endoscope; and

FIG. 24 is an illustration to explain a capsule-type endoscope system inwhich a marking can be displayed by analyzing the position where the tipof the puncture needle will make contact with a living tissue surface,based on the positional relationship between the puncture needleprojection port, the living tissue, and the moving direction of thepuncture needle.

DETAILED DESCRIPTION

In the present invention, a capsule-type endoscope is provided with animage pickup unit that includes an objective optical system, an imagepickup element, and an illumination light source. A transparent cover,that is transparent within the field of view of the objective opticalsystem, seals these components within an external surface. At leastwithin the field of view of the objective optical system, the innersurface of the transparent cover is spherical so as to have a center ofcurvature, the optical axis of the objective optical system is offsetfrom the center of curvature of the transparent cover, and the followingCondition (1) is satisfied:0.01<L 1/R tan θ<0.5   Condition (1)where

L1 is the distance between the center of curvature of the inner surfaceof the transparent cover and the optical axis of the objective opticalsystem;

R is the radius of curvature of the inner surface of the transparentcover; and

θ is the half-field angle of the objective optical system.

It is preferred in the capsule-type endoscope of the present inventionthat the light emitting surface(s) of the light sources that form anillumination means are positioned in a manner such that the lightemitting surface(s) does (do) not overlap an image of the entrance pupilof the objective optical system when light rays are projected onto aplane Qm by being reflected by the inner surface of the transparentcover, where the plane Qm is defined as the plane containing the lightemitting surface(s) of the illumination means.

Furthermore, the capsule-type endoscope of the present invention ischaracterized by the fact that the optical axis of the objective opticalsystem is non-orthogonal to the tangential plane of the inner surface ofthe transparent cover where it intersects same (hereinafter referred tosimply as ‘not orthogonal to the inner surface of the transparentcover’), and at least one of the components of the image pickup unit istilted so as to be non-orthogonal to the optical axis of the objectiveoptical system or is de-centered relative to other components of theimage pickup unit.

The present invention provides a capsule-type endoscope that can preventlight that is reflected by the inner surface of the transparent coverfrom causing flare in the objective optical system, even in the casewhere the capsule size is reduced or while ensuring that there exists aspace for mounting either a tank for carrying a substance in liquid formor a battery for increasing the operating time of the capsule-typeendoscope. The present invention will first be discussed in generalterms with reference to FIGS. 1(a) and 1(b).

FIGS. 1(a) and 1(b) are sectional illustrations of a capsule-typeendoscope according to one embodiment of the present invention as viewedfrom the side and front, respectively. In FIGS. 1(a) and 1(b), item 4 isthe optical axis of the objective optical system 3, and St is the vertexof the inner surface 10 of the transparent cover 8. Here, the vertex Stis a point on the inner surface 10 of the transparent cover 8 at whichthe distance between two points Gn and En is largest. Gn is a point onthe inner surface 10 of the transparent cover 8 and En is theintersection of a normal from the point Gn to a plane that is orthogonalto the optical axis and tangential to the most object side surface(surface being nearest to an object) of the objective optical system 3.Item 9 is the outer surface of the transparent cover, P(Pc) is thecenter of the entrance pupil of the objective optical system 3, and P′cis the point of intersection of hypothetical light rays if emitted fromthe center Pc of the entrance pupil and reflected by the inner surface10 of the transparent cover 8. Qm is as defined above, namely, the planecontaining the light emitting surface(s) of the illumination means, X isthe point of intersection of a line drawn from the vertex St of theinner surface of the transparent cover normal to the plane Qm, and P′ isthe point of intersection of a normal line drawn from the point P′c tothe plane Qm. Region 15 (herein termed the reflected image of theentrance pupil of the objective optical system) is defined by the outerlimit of hypothetical light rays emitted from the center of the entrancepupil of the objective optical system 3, when such hypothetical lightrays are then reflected by the inner surface 10 of the transparent cover8 so as to be incident onto the plane Qm.

The capsule-type endoscope shown in FIGS. 1(a) and 1(b) is an embodimentof the present invention in which the inner surface 10 of thetransparent cover 8 is spherical. In the capsule-type endoscope shown inFIGS. 1(a) and 1(b), the objective optical system 3 is provided with thecenter Pc of its entrance pupil on a line 17 (in the plane Qm) thatpasses through the center of curvature 11 of the inner surface 10 of thetransparent cover 8 and is orthogonal to the optical axis 4 of theobjective optical system 3. In FIG. 1(a), the dashed lines 7′, 7′ definethe outer limits of the field of view of a prior art capsule-typeendoscope in which the center Pc of the entrance pupil of the objectiveoptical system 3 coincides with the center of curvature 11 of the innersurface 10 of the transparent cover 8. On the other hand, the solidlines 7, 7 define the outer limits of the field of view of the objectiveoptical system 3 when the center Pc of the entrance pupil of theobjective optical system 3 is provided at a point that is laterallyoffset from the center of curvature 11, and when the above Condition (1)is satisfied.

The outer surface 9 of the transparent cover 8 has its center ofcurvature at 12. In the capsule-type endoscope shown in FIGS. 1(a) and1(b), the centers of curvature 11 and 12 of the inner and outer surfaces10 and 9 of the transparent cover 8 coincide.

Satisfying Condition (1) above enables the cross-section size of thecapsule to be reduced by the area indicated by the shaded part in FIG.1(b) while maintaining the same field of view of the objective opticalsystem as in prior art capsule-type endoscopes.

Further, the light emitting surface(s) of the illumination means 13 does(do) not overlap the reflected image 15 of the entrance pupil of theobjective optical system 3 on the plane Qm, as can be seen in thecapsule-type endoscope shown in FIGS. 1(a) and 1(b). Thus, illuminationlight emitted from the illumination means 13 and reflected by the innersurface of the transparent cover 8 does not reach the entrance pupil ofthe objective optical system 3, thereby preventing flare.

When the upper limit of Condition (1) above is not satisfied, theobjective optical system 25 3 is too close to the vertex St of the innersurface 10 of the transparent cover 8, failing to reserve a space forproviding the illumination light source. On the other band, when thelower limit of Condition (1) is not satisfied, the objective opticalsystem 3 is too far away from the vertex St of the inner surface 10 ofthe transparent cover 8, unfavorably increasing the entire capsulelength.

It is preferred in the capsule-type endoscope of the present inventionthat the objective optical system be provided in a manner such that itsoptical axis is non-orthogonal to the inner surface of the transparentcover, and at least one of the components of the image pickup unit istilted so as to be non-orthogonal to the optical axis of the objectiveoptical system or is de-centered relative to other components of theimage pickup unit.

FIG. 2 is an illustration to explain another important feature of thecapsule-type endoscope of the present invention. It shows object pointson the outer surface 9 of the transparent cover 8 at the outer limits ofthe field of view of the objective optical system 3 (in a cross sectionthat contains the optical axis 4 of the objective optical system 3 andthe vertex St of the inner surface 10 of the transparent cover 8) beingimaged by the objective optical system 3.

Unlike conventional endoscopes, the capsule-type endoscope of thepresent invention does not have a mechanism for sending air into theorgan during observation/diagnosis. Therefore, the digestive tract(i.e., the usual passageway of the capsule endoscope) is presumablycontracted and thus at least partially blocks the field of view of theobjective optical system of the capsule-type endoscope. In addition,when the capsule is moved within a living body (hereinafter sometimesreferred to simply as a ‘body’) by means of peristaltic motion of atubular organ, the capsule is subjected to uniform pressure by the innerwall of the tubular organ. The inner wall of the tubular organ is incontact with the outer surface of the capsule in the most stable mannerand the inner wall of the tubular organ also surrounds the outer surfaceof the transparent cover along its curved surface. Therefore, it isdesired that the image pickup unit be able to focus on an object pointthat is located on the outer surface 9 of the transparent cover 8.

The image pickup unit 1 may be formed of an objective optical system 3having lens components 5, 5 (which, as shown, may each consist of a lenselement), a diaphragm (not shown), a lens frame (not shown), a spacingring (not shown), an image pickup element 2, and an image pickup elementframe (not shown).

As shown in FIG. 2, when the objective optical system 3 is positionedwith the center of its entrance pupil shifted from the centerline of thecapsule so that the optical axis of the objective optical system 3 isnon-orthogonal to the inner surface of the transparent cover 8, thedistance between the most object-side surface of the objective opticalsystem 3 and the outer surface 9 of the transparent cover 8 varies,depending on the direction of viewing. This results in a shifting of theimage position for each object point. Therefore, if the image pickupsurface of the image pickup element 2 is orthogonal to the optical axisof the objective optical system as in prior art capsule-type endoscopes,an object of interest, such as the inner surface of a tubular organ thatis in contact with the outer surface of the transparent cover 8, willhave a portion that is not properly focused onto the surface of theimage pickup element, and this will cause difficulty in observation.

In the capsule-type endoscope shown in FIG. 2, the image pickup element2 is tilted so as to be non-orthogonal to the optical axis of theobjective optical system 3 in such a manner that the image pickupsurface is positioned at the image positions XN1′, XN2′ that correspondto the distances XN1, XN2 between the most object-side surface of theobjective optical system 3 and the outer surface 9 of the transparentcover 8. In this way, focal shifts as a result of differences in theobject point distance to the outer surface 9 of the transparent cover 8in different viewing directions is corrected. In this manner, asmall-sized, capsule-type endoscope that allows for clear observationsof an object, such as the inner wall of a tubular organ, that is incontact with the outer surface 9 of the transparent cover 8 can beprovided.

In lieu of, or in addition to, the image pickup unit being tilted asshown in FIG. 2, at least one of the components of the image pickup unitother than the image pickup element can be de-centered relative to othercomponents of the image pickup unit. In this way, focal shifts as aresult of differences in the object distance to the outer surface 9 ofthe transparent cover 8 in different viewing directions can be similarlycorrected and clear images can be obtained.

Various embodiments of the capsule-type endoscope of the presentinvention will now be described in detail with reference to thedrawings.

Embodiment 1 and Two Possible Modifications

FIGS. 33(a) and 33(b) are illustrations which show the front portion ofa capsule-type endoscope according to Embodiment 1 of the presentinvention, with FIG. 3(a) being a cross-section of a front portion ofthe capsule-type endoscope as viewed from the side, and FIG. 3(b) beinga cross-section of a front portion of the capsule-type endoscope asviewed from the front. Like items in the drawings have been similarlynumbered throughout the drawings. The illumination means 13 may beformed of semiconductor-chip-type, light emitting diodes (hereinaftertermed LEDs), that are provided at different positions within thecapsule, and the capsule-type endoscope is provided with a cover that istransparent within the field of view of the objective optical system 3and that seals the capsule. The entrance pupil of the objective opticalsystem 3 coincides with the most object-side surface of the lenscomponents 5, 5 that form the objective optical system 3. Furthermore,the entrance pupil plane is on the same plane as the plane Qm thatcontains the light emitting surface(s) of the illumination means 13. Apower supply battery and a transmission antenna for transmittinginformation, such as images, to a separate receiver device (not shown)are provided behind (i.e., on the image side of) the objective opticalsystem 3.

As in FIG. 1, the inner surface 10 of the transparent cover 8 isspherical, and the center of curvature 11 of the inner surface 10 of thetransparent cover 8 is on a line 17 that passes through the center Pc ofthe entrance pupil of the objective optical system 3 and is orthogonalto the optical axis 4 of the objective optical system 3. The lines 7, 7are drawn through the center of the entrance pupil of the objectiveoptical system 3 so as to pass through the points Sm and Sn that arelocated on the inner surface 10 of the transparent cover and these linesdefine the outer limits of the field of view of the objective opticalsystem 3.

As mentioned above, the size of the capsule can be reduced relative tothat of prior art capsule-type endoscopes by offsetting the optical axisof the objective optical system from the axial center of the capsule. Inthis embodiment, the offset amount is 0.76 mm for a prior arttransparent cover having an outer diameter of 5.6 mm. In this way, thecross-sectional area of the capsule can be reduced (as shown by thehatched area illustrated in FIG. 33(b)) and the outer diameter of thecapsule's cylindrical surface can be reduced from 5.6 mm to 5.0 mm. Thereflected image range 15 of the entrance pupil of the objective opticalsystem is defined herein as the intersection points with the plane Qm ofhypothetical light rays that emerge from the center Pc of the entrancepupil of the objective optical system at the outer limits of the fieldof view of the objective optical system and are then reflected by theinner surface of the transparent cover onto the plane Qm.

The reflected image range 15 (defined above) may be determined byreverse ray tracing light rays entering the center Pc of the entrancepupil of the objective optical system 3 from points on the inner surfaceof the transparent cover 8 that are at the outermost periphery of thefield of view. In other words, in FIG. 33(a), the reflected image range15 of the entrance pupil of the objective optical system 3 is determinedby the light rays 7 that form the outer limits of the field of view ofthe objective optical system, if such rays were to be reversed,reflected by the inner surface 10 of the transparent cover 8, and werethen to be incident onto the plane Qm.

In the capsule-type endoscope of Embodiment 1, four LEDs comprise theillumination means 13 and these LEDs are provided outside the reflectedimage range 15 of the entrance pupil of the objective optical system 3.In addition, none of the optical axes of the LEDs is orthogonal to theinner surface 10 of the transparent cover 8. The optical axis of each ofthe four LEDs passes through the center of its light-emitting surfaceand is orthogonal to the light-emitting surface. When multiple lightemitting surfaces form the illumination means 13, and when thesesurfaces do not lie in the same plane Qm, the objective optical system 3and each LED are positioned to satisfy Condition (1) above within therespective planes containing the light emitting surfaces of theillumination means 13.

With the capsule-type endoscope of Embodiment 1 having the structurediscussed above, a capsule-type endoscope can be provided that isreduced in size relative to that of prior art capsule-type endoscopes,while ensuring the same field of view. Moreover, light emitted from theillumination means 13 and reflected by the inner surface of thetransparent cover 8 can be prevented from entering the entrance pupil ofthe objective optical system 3. Therefore, flare can be prevented so asto allow for observation of clear images.

FIGS. 4(a) and 4(b) show a first possible modification to Embodiment 1,with FIG. 4(a) being a cross-section of a front portion of thecapsule-type endoscope as viewed from the side, and FIG. 4(b) being across-section of a front portion of the capsule-type endoscope as viewedfrom the front. In the capsule-type endoscope of the modification toEmbodiment 1 shown in FIGS. 4(a) and 4(b), one of the illumination lightsources (such as the illumination light source 13a) is provided with itsoptical axis orthogonal to the inner surface 10 of the transparent cover8. This modification to Embodiment 1 will now be discussed in comparisonwith a prior art capsule-type endoscope having a transparent coverdiameter of 8.3 mm, as indicated by the dashed lines in FIG. 4(a). Byoffsetting the optical axis of the objective optical system from theaxial center of the capsule a distance of 1.7 mm, the outer diameter ofthe capsule's cylindrical surface can be reduced from 8.3 mm to 7.4 mm.As before, the lines 7, 7 are drawn through the center of the entrancepupil of the objective optical system 3 so as to pass through the pointsSm and Sn that are located on the inner surface 10 of the transparentcover 8 and that define the outer limits of the field of view of theobjective optical system 3.

FIGS. 5(a) and 5(b) show a second possible modification to Embodiment 1,with FIG. 5(a) being a cross-section of a front portion of thecapsule-type endoscope as viewed from the side, and FIG. 5(b) being across-section of a front portion of the capsule-type endoscope as viewedfrom the front. With the second possible modification to Embodiment 1 asshown in FIGS. 5(a) and 5(b), a space for mounting other members can beobtained without increasing the capsule size as compared with a priorart capsule-type endoscope. As a result, a capsule-type endoscope can beobtained that has space for a tank 18 for carrying a substance in liquidform while preventing light that is reflected by the inner surface ofthe transparent cover 8 from entering the entrance pupil of theobjective optical system and causing flare. Instead of a tank for acarrying a substance in liquid form being mounted in the space formounting other members, one of a battery to extend the operation time ofthe capsule endoscope, a wireless transmission/reception means, or acapacitor can be mounted. Other structures remain the same as for thecapsule-type endoscope shown in FIGS. 33(a) and 33(b), and thereforefurther explanation will be omitted. The capsule-type endoscope of thismodified embodiment allows for providing one of a substance in liquidform (such as a coloring agent or a drug) to a lesion, an extendedoperating time of the image pickup system, improved reliability of thewireless communications, or another power source (such as a capacitor)within a small-sized, capsule-type endoscope.

In the case where a tank for delivery of a substance in liquid form to alesion is provided, the capsule endoscope exterior is provided with anozzle for spraying the substance in liquid form. When a possible lesionis found by observing the inner wall of an organ that is in the field ofview of the objective optical system while the capsule-type endoscopemoves along within tubular organs such as organs of the digestive tract,a substance such as a coloring agent can be sprayed on the regionthrough the nozzle. Therefore, a jet orifice of the nozzle is directedin the viewing direction, and the field of view of the objective opticalsystem and the spray range of the nozzle should overlap. It is furtherdesired that the nozzle be at a position that does not obscure theobservation of a target region within the field of view.

FIG. 6 is an illustration to show the positional relationships withinthe outer limits 7, 7 of the field of view of the objective opticalsystem 3, a jet orifice of a nozzle 30 for applying a substance inliquid form, and an observation target region 32 of the capsule-typeendoscope 40 of the modification to Embodiment 1 shown in FIGS. 5(a) and5(b). Presumably, the inside of a tubular organ (such as the smallintestine, though which the capsule-type endoscope 40 passes) contactsthe peripheral portion of the transparent cover of the capsule-typeendoscope 40. The capsule-type endoscope 40 is moved along through thetubular organ by means of the peristaltic motion of the tubular organ.Therefore, a part of the outer surface 9 of the transparent cover 8 isin contact with the inner wall 33 of the tubular organ and is within thefield of view of the objective optical system 3.

The capsule-type endoscope shown in FIG. 6 is designed to expand theinner wall 33 of the tubular organ through which it passes for enablinga substance in liquid form to be sprayed onto the inner wall of thetubular organ. As shown in FIG. 6, which illustrates a cross-section ofthe capsule-type endoscope as viewed from the side, a jet orifice 31 ofthe nozzle 30 is provided outside the field of view of the objectiveoptical system 3. In addition, if the angle β between the centerline ofthe jet orifice 31 and the optical axis 4 of the objective opticalsystem 3 is made to lie in the range of 15° to 75°, the nozzle and jetorifice can be relatively near the optical axis of the objective opticalsystem 3, as indicated by a nozzle 30′ and a jet orifice 31′ as shown indashed lines. A substance in liquid form is pushed out from the tank 18to the nozzle 30 by a spray control device associated with the tank.Liquid is ejected from the jet orifice 31 and sprayed onto theobservation target region 32 within a region delimited by the mid-pointand the far point of the depth of field.

If the angle β is smaller than 15°, the spray target region and the jetorifice 31 are too distant from each other; therefore the liquidsubstance will be sprayed onto an excessively large region, therebyfailing to put sufficient spray per unit area on the target region. Onthe other hand, if β is larger than 75°, the spray target region and thejet orifice 31 are too close to each other; therefore, the spray willcontact the outer surface 9 of the transparent cover 8 and portions ofthe target region will be insufficiently sprayed.

The nozzle shown in FIG. 6 is provided outside of the field of view ofthe objective optical system. However, the nozzle can be positioned sothat at least a portion of the nozzle is within the field of view, ifthis does not interfere with the observation of a target region withinthe field of view. This is actually the preferred situation since itallows the spraying of the substance in liquid form to be observedwithin the field of view. In such a case, it is desired that the nozzlesurface be processed so as to reduce the amount of light reflected bythe nozzle. Alternately, a light absorbing black coating can be appliedto the nozzle surface so that illumination light that would otherwise bereflected by the nozzle and cause flare within the field of view isminimized.

FIG. 7 shows an embodiment of the capsule-type endoscope in which thejet orifice of the nozzle is positioned within the field of view of theobjective optical system. The jet orifice 31 of the nozzle 30 of thecapsule-type endoscope shown in FIG. 6 is provided at a position that iswithin the field of view of the objective optical system 3 and where itdoes not interfere with the observation of a target region within thefield of view. As shown in FIGS. 22(a) and 22(b), the nozzle 30 and tank18 can be formed as a unit that is detachably attachable to thecapsule-type endoscope. In this way, the tank may be easily filled witha substance in liquid form, such as a solution. Further, when deliveryof a substance to a target region is not required, the tank can beremoved and, in its place, an extra power unit 42 can be mounted forprolonged observations.

A capsule-type endoscope may be provided with a delivery tube having apuncture needle at one end that can be used when a substance in liquidform (such as a coloring agent or a drug) is desired to be injected intoa living tissue. In such a case, the puncture needle is penetrated intothe living tissue at a position that is within the field of view of theobjective optical system, and the substance in liquid form is injectedvia the delivery tube from the tank within the capsule. To accomplishthis, a projection port for the puncture needle should be positionedwithin the field of view of the objective optical system so that the tipof the puncture needle can be observed before the tip of the punctureneedle is inserted into the living tissue. This is to ensure that thepuncture needle tip does not puncture at an unintended point and toensure that the puncture needle tip does not extend entirely through,and thus beyond, the intended living tissue. A similar precaution can betaken for a puncture needle to be inserted into living tissue forcollecting biopsy samples.

FIG. 8 shows an exemplary structure of a capsule-type endoscope that isprovided with a solution delivery tube having a puncture needle at oneend of the solution delivery tube. In the capsule-type endoscope in FIG.8, a projection port 34 for the puncture needle is provided at aposition that is outside the outer limits 7 of the field of view of theobjective optical system 3, but the tip of the puncture needle 35 isinside the field of view so that the insertion position of the punctureneedle may be observed before the puncture needle is actually insertedinto the living tissue. The puncture needle projection port 34 isdesigned to expand the inner wall 33 of a tubular organ, and therebycreate an empty space between the puncture needle projection port 34 andthe observation target region 32 that is within the field of view of theobjective optical system.

With such a structure, the positional relationship between the punctureneedle 35 and the observation target region 32 of the living tissue maybe determined before the tip of the puncture needle 35 is inserted intothe observation target region 32. Therefore, the puncture needle tip maybe prevented from puncturing the living tissue at an unintended point,and the puncture needle tip may be prevented from extending entirelythrough the living tissue. The puncture needle 35 may be stored insidethe capsule and pushed out of the projection port 34 by a mechanism whenthe capsule-type endoscope approaches the observation target region 32within the outer limits 7 of the field of view. Moreover, the punctureneedle 35 is provided with markings, which may be in different colors,at regular intervals from its tip that may be observed via a monitor todetermine the depth that the tip of the puncture needle 35 has beeninserted into the observation target region 32.

As shown in FIGS. 23(a) and 23(b), the projection port 34 of thepuncture needle, a puncture needle storage part 44, and a mechanism 37for pushing out the puncture needle may be formed as a unit that may bedetachably attached to the capsule-type endoscope. In such a case, it ispreferred that an electrical connection 38 be provided at the jointbetween the capsule and the detachable unit so that power is suppliedfrom the capsule to the mechanism 37 for pushing out the punctureneedle.

FIG. 9 is an illustration to show another exemplary structure of anozzle 30, as well as of a puncture needle projection port 34. In thisstructure, the nozzle 30 and the puncture needle projection port 34project through the transparent cover 8. The nozzle 30 is connected tothe tank 18 through the transparent cover 8 at a position that isoutside the outer limits 7, 7 of the field of view of the objectiveoptical system. A jet orifice 31 is provided within the outer limits 7,7 of the field of view of the objective optical system. The punctureneedle projection port 34 is positioned so that the puncture needleprotrudes through the transparent cover 8 at a point that is outside theouter limits 7, 7 of the field of view of the objective optical system.A delivery tube 36 that is connected to the puncture needle 35 may beconnected to another tank (not shown). The front surface of thetransparent cover 8 is designed so that a space exists between thepuncture needle projection port 34 and the observation target region 32of the living tissue. This enables the positional relationship betweenthe puncture needle 35 and the living tissue to be observed. It isdesired that the positional relationship between the image pickup unitand the inner surface of the transparent cover 8 satisfy Condition (1)above, but this is not required.

FIG. 10 is an illustration to explain the operation of a capsule-typeendoscope system for observing the inner wall of the digestive tract. InFIG. 10, the equipment enclosed by the dotted lines is an image displaysystem 25 that is provided externally of the patient. A patient 41 isdressed in specifically designed clothing for externally controlling theorientation of the capsule-type endoscope 40 moving within the digestivetract 21. For example, electromagnetic induction units, not shown in thefigure, may be used for this purpose. Image signals that are wirelesslytransmitted from a communication unit that is positioned within thecapsule-type endoscope 40 are received by a communication device 22 thatis provided externally of the patient. The communication device 22 maybe connected to a personal computer 24 for processing the image signals.The images that are processed by the personal computer 24 may bedisplayed on a monitor 23. The personal computer 24 is also providedwith a memory device for storing the image signals. For example, atarget symbol 26 can be marked at a point (“x” in the figure) where thecenterline of the jet orifice 31 intersects an object to be viewed(i.e., the inner wall of the digestive tract 21). In this manner, onecan ensure that a substance in liquid form is accurately sprayed onto anobservation target region 32 (such as a possible lesion) within thefield of view of the objective optical system.

During an observation while the capsule-type endoscope 40 proceeds alongwithin the digestive tract 21, the observation target region 32 iscaptured by the image pickup unit between the far point and the midpoint of the depth of field of the objective optical system. Theorientation of the capsule-type endoscope 40 may be controlled so thatthe target symbol 26 overlaps the observation target region 32. A seriesof operations, including the display of the target symbol 26, theorientation control of the capsule-type endoscope 40, and the sprayingof a substance in liquid form can be executed using one or more of akeyboard, a mouse, and a joy stick that are connected to the personalcomputer 24.

The personal computer 24 may be used for tracking and controlling thecapsule-type endoscope. For example, the personal computer 24 mayfunction to automatically control a series of operations, such asautomatic tracking of the capsule-type endoscope and the delivery of asubstance that is sprayed onto an intended target region. With thepersonal computer 24 providing such a function, an observer may viewimages from the capsule-type endoscope that are displayed on the monitor23 and may move a cursor over the observation target region 32 so as tospecify automatic tracking of a target and the commencement of anautomatic spray function. Alternatively, the personal computer 24 mayprovide the function of analyzing the morphology and color tone of anobject captured by the image pickup unit. Screening for particularlesion patterns stored in the memory of the personal computer 24 may beperformed concurrently with image processing and automatic targettracking. A substance in liquid form (such as a coloring agent or adrug) may be sprayed from the jet orifice 31 when the observation targetregion 32 and the target symbol 26 overlap on the monitor 23 in thecourse of automatic tracking. When automatically determining a trackingtarget by analyzing the morphology and color tone of the images capturedby the image pickup unit, an indication to draw the observer's attentionmay be displayed on the monitor 23 when a lesion that may become atracking target is first identified.

Should an observer determine by observing the received images that thereis no need for spraying, the observer can cancel the automatic trackingoperation by, for example, using a keyboard that is connected to thepersonal computer 24. When using a capsule-type endoscope that isprovided with a delivery tube and a puncture needle, the personalcomputer 24 may be provided with an image processing function so as todetermine from captured images the depth that a puncture needle has beeninserted into a living tissue after it first contacts the surface of aliving tissue and so as to display the result on a monitor. Furthermore,a marking 39 (such as an “x”) can be displayed at a position where thetip of the puncture needle will make contact with the living tissuesurface, based on the positional relationship between the punctureneedle projection port 34, the position of the observation target region32 of the living tissue and the moving direction of the puncture needle.

As shown by the diagonal, broken lines in the region 32′ of FIG. 6, theobservation target region 32 that is sprayed with a substance graduallyapproaches the objective optical system 3 and makes contact with theouter surface 9 of the transparent cover 8 near the near point of thedepth of field of the objective optical system 3. Therefore, it isdesired that the image pickup unit 1, which includes the objectiveoptical system 3 and the image pickup element 2, has its highestresolution for objects near the outer surface 9 of the transparent cover8 so that the region 32′ can be viewed very clearly and a diagnosis madeof the region 32′. In other words, it is desired for the structure inFIG. 6 to satisfy the following Conditions (2) and (3):R1≅5 lines per mm   Condition (2)R2≧1 line per mm   Condition (3)where

R1 is the resolution on the optical axis at positions between the mostobject-side surface of the objective optical system and the point ofintersection of the optical axis of the objective optical system withthe outer surface of the transparent cover; and

R2 is the resolution, as will be defined below, on the optical axis atpositions between the most object-side surface of the objective opticalsystem and the far point of the depth of field of the objective opticalsystem.

The term “resolution” (as will be defined below) is measured as follows.Pairs of black and white lines are captured by the image pickup unit anddisplayed on a monitor via a system for processing image signalstransmitted from the solid-state image pickup element. The contrast I ofthe black/white line pairs on the monitor is obtained using thefollowing Equation (A):I=(Imax−Imin)/(Imax+Imin)   Equation (A)where

Imax and Imin are the maximum and minimum values of the black and whiteintensity profile, respectively.

‘Resolution’ is defined as the reciprocal of the width (in mm) of theblack/white line pair when the contrast I, as set forth above, is 10%.Thus, “a resolution of 5 lines/mm or higher” means that the contrast ofblack/white line pairs having a width of 0.2 mm is 10% or more on themonitor. Similarly, a resolution of 1 line/mm or higher means that thecontrast of black/white line pairs having a width of 0.5 mm is 10% ormore on the monitor. When the image pickup unit 1 has a resolution of 5lines/mm or higher for an object point distance A1, the living tissuenear the outer surface of the transparent cover can be enlarged on themonitor 23 for observation. Particularly, it is important for acapsule-type endoscope to allow for close-up observation of villi, whichare small projections that extend from the wall of the small intestine.Villi are approximately 0.2 to 0.5 mm in width; therefore a resolutionhigher than this is required for good observation. When the image pickupunit 1 has a resolution of 1 line/mm or higher for an object pointdistance B1, the observation target region 32 can be easily found at thefar point of the field of view when displayed on the monitor 23.

It is desired that the image pickup unit 1 is provided with an imagepickup element 2 and objective optical system 3 that satisfies thefollowing Conditions (4)-(6):80<IH/P<500   Condition (4)80<FL/P<500   Condition (5)400<Fno/P<3000   Condition (6)where

IH is the distance (in mm) between the center and the point most distantfrom the center of the effective image pickup area of thelight-receiving surface of the image pickup element;

P is the horizontal pixel pitch (in mm) of the image pickup element;

FL is the focal length (in mm) of the objective optical system; and

Fno is the effective F-number of the objective optical system.

When the value of IH/P equals or exceeds 500 (i.e., does not satisfy theupper limit of Condition (4)), a larger depth of field cannot beobtained when used in combination with the objective optical system. Onthe other hand, when the value of IH/P does not satisfy the lower limitof Condition (4), a required resolution cannot be obtained near the nearpoint of the depth of field.

When the value of FL/P equals or exceeds 500 (i.e., does not satisfy theupper limit of Condition (5)), the depth of field will become small whenused in combination with the objective optical system. On the otherhand, when the value of FL/P does not satisfy the lower limit ofCondition (5), it is difficult to obtain a desired resolution at theobject point distance A1.

When the value of Fno/P equals or exceeds 3000 (i.e., does not satisfythe upper limit of Condition (6)), the required resolution will exceedthe optical diffraction limit, and thus high quality images will beunattainable even though the images are in focus. When the value ofFno/P is 400 or less (i.e., does not satisfy the lower limit ofCondition (6)), the depth of field will become small; a desiredresolution will be obtained at the object point distance A1 while focalshifts will occur at the object point distance B1.

For example, it is preferred for a capsule-type endoscope having anouter diameter of approximately 10 mm to have an object point distanceA1 of 3 mm and an object point distance B1 of 50 mm. The objectiveoptical system 3 consists of two positive lens elements in the disclosedembodiments of the present invention. However, the objective opticalsystem 3 of the capsule-type endoscope of the present invention is notrestricted to such a lens structure.

Embodiment 2 and Three Possible Modifications

FIGS. 11(a)-14(b) are illustrations of cross-sections of the frontportion of the capsule-type endoscope according to Embodiment 2, andthree possible modifications to Embodiment 2, of the present invention.FIG. 11(a) is a cross-section of a front portion of the capsule-typeendoscope of Embodiment 2 as viewed from the side, and FIG. 11(b) is across-section of a front portion of the capsule-type endoscope ofEmbodiment 2 as viewed from the front.

In the capsule-type endoscope of Embodiment 2 shown in FIGS. 11(a) and11(b), the inner surface 10 of the transparent cover 8 is spherical. Thecenter of curvature 11 of the inner surface 10 of the transparent cover8 is on the object side of a line 17 that passes through the center Pcof the entrance pupil of the objective optical system 3 and isorthogonal to the optical axis 4 of the objective optical system 3. Theobjective optical system 3 is provided in such a manner that theentrance pupil thereof is in the same plane as a plane Qm that containsthe light emitting surface(s) 14 (see FIG. 12(a)) of the illuminationlight source(s) that form the illumination means 13.

Furthermore, in the capsule-type endoscope of Embodiment 2 shown inFIGS. 11(a) and 11(b), the objective optical system 3 is positioned sothat the point of intersection X with the plane Qm of a line drawn fromthe vertex St of the inner surface 10 of the transparent cover so as tobe perpendicular to the plane Qm lies on the longitudinal axis of thecapsule, and the point X is on a line that connects the intersectionpoints P and P′. Points that happen to be coincident in the figures arelabeled with multiple labels, with the second label listed inparenthesis. P is the intersection with a plane Qm of a line drawn fromthe center Pc of the entrance pupil of the objective optical system 3 soas to be perpendicular to the plane Qm. Thus, in FIG. 11(a), P and Pcare coincident and the position thereof is labeled P(Pc). P′ is theintersection with the plane Qm of a line drawn from the intersectionpoint P′c so as to be perpendicular to the plane Qm. P′c is theintersection point of hypothetical light rays that emerge from thecenter Pc of the entrance pupil of the objective optical system 3 andare reflected by the inner surface 10 of the transparent cover 8 at thepoints Sm and Sn that define the outer limits of the field of view ofthe objective optical system 3 in the plane (depicted in FIG. 11(a))that contains the vertex St of the inner surface of the transparentcover and the optical axis of the objective optical system. In thisembodiment, three illumination light sources of the illumination means13 are provided outside the reflected image range 15 of the entrancepupil of the objective optical system 3 when the image of the entrancepupil is projected via the inner surface 10 of the transparent cover 8back onto the plane Qm.

FIGS. 12(a) and 12(b) show a first possible modification to Embodiment2, with FIG. 12(a) being a cross-section of a front portion of thecapsule-type endoscope according to the first possible modification ofEmbodiment 2 as viewed from the side, and FIG. 12(b) being across-section of a front portion of the capsule-type endoscope accordingto the first possible modification of Embodiment 2 as viewed from thefront. In this capsule-type endoscope, the inner surface 10 of thetransparent cover 8 is spherical. The center of curvature 11 of theinner surface 10 of the transparent cover 8 is on the image side of aline 17 that passes through the center Pc of the entrance pupil of theobjective optical system 3 and is orthogonal to the optical axis 4 ofthe objective optical system 3. The objective optical system 3 ispositioned so that the entrance pupil plane thereof lies in the sameplane as the plane Qm that contains the light emitting surfaces 14 ofthe illumination light sources that form the illumination means 13.

Furthermore, in the possible modification to Embodiment 2 shown in FIGS.12(a) and 12(b), the objective optical system 3 is positioned such thatthe intersection X with the plane Qm of a line drawn from the vertex Stof the inner surface 10 of the transparent cover perpendicular to theplane Qm is on a line that connects the points P and P′, where Qm, P andP′ are as previously defined. In the possible modification shown inFIGS. 12(a) and 12(b), three illumination light sources form theillumination means 13 and these illumination light sources are providedoutside the reflected image range 15 of the entrance pupil of theobjective optical system 3.

In the capsule-type endoscope of the present invention according toEmbodiment 2 shown in FIGS. 11(a) and 11(b), and the first possiblemodification shown in FIGS. 12(a) and 12(b), four areas are defined bythe lines 7 m and 7 n that lie within a plane that contains the opticalaxis 4 of the objective optical system 3 and the vertex St of the innersurface 10 of the transparent cover 8. The lines 7 m and 7 n are drawnthrough the center of the entrance pupil of the objective optical system3 so as to pass through the points Sm and Sn on the inner surface 10 ofthe transparent cover 8 that define the outer limits of the field ofview of the objective optical system in the cross-section (depicted inFIG. 12(a)) that contains the vertex St of the inner surface of thetransparent cover and the center Pc of the entrance pupil of theobjective optical system. As is apparent from FIG. 12(b), the center ofcurvature 11 of the portion of the inner surface 10 of the transparentcover 8 that is within the field of view of the objective optical system3 is in a sector (among the four sectors delineated by the intersectionof lines 7 m and 7 n when these lines are extended backward as shown inFIG. 12(a)) that does not include the optical axis of the objectiveoptical system 3. In the capsule-type endoscope of Embodiment 2 and thefirst possible modification as discussed above, the center of curvature11 of the inner surface 10 of the transparent cover 8 coincides with thecenter of curvature of the portion of the inner surface 10 of thetransparent cover 8 that is within the field of view of the objectiveoptical system 3. Among the four sectors delineated by the intersectionof the lines 7 m and 7 n when these lines are extended backward as shownin FIG. 12(a), when the center of curvature 11 of the inner surface 10of the transparent cover 8 lies within a sector that includes theoptical axis 4 of the objective optical system 3, the reflected imagerange 15 (defined above) of the entrance pupil of the objective opticalsystem 3 will be larger than desired and thus will not leave asufficient space for providing the illumination light source(s) thatform the illumination means 13.

This issue will now be discussed with reference to FIGS. 15(a) to 16(b).FIGS. 15(a) and 15(b) are illustrations to show exemplary structure of acapsule-type endoscope according to the present invention so as toclarify the differences between the present invention versus prior artcapsule-type endoscopes, with FIG. 15(a) being a cross-section of afront portion of the capsule-type endoscope as viewed from the side, andFIG. 15(b) being a cross-section of a front portion of the capsule-typeendoscope as viewed from the front.

In the capsule-type endoscope shown in FIGS. 15(a) and 15(b), the centerof curvature 11 of the inner surface 10 of the transparent cover 8 is ina sector (among the four sectors delineated by the intersection of thelines 7 m and 7 n when these lines are extended backward as shown inFIG. 15(a)) that contains the optical axis of the objective opticalsystem 3 and is on the object side of the center Pc of the entrancepupil of the objective optical system 3. As before, the lines 7 n and 7m are drawn from the center of the entrance pupil of the objectiveoptical system to the points Sn and Sm that define the outer limits ofthe field of view of the objective optical system cross-section(depicted in FIG. 15(a)) that contains the vertex St of the innersurface of the transparent cover and the center Pc of the entrance pupilof the objective optical system. Therefore, the line 7 m is on the imageside (i.e., is to the right in FIG. 15(a)) of the line 19 m thatconnects the center of curvature 11 to the outer boundary point Sm, andthe line 7 n is on the image side of the line 19 n that connects thecenter of curvature 11 to the outer boundary point Sn (Sm and Sn are asdefined previously). Once again it is assumed that hypothetical lightrays come from the center Pc of the entrance pupil of the objectiveoptical system 3 and are reflected at the outer boundary points Sm andSn of the field of view in the plane of FIG. 15(a). The light reflectedat the point Sm proceeds toward the object side (i.e., to the left inFIG. 15(a)) of the line 19m that connects the center of curvature 11 tothe outer boundary point Sm. The light reflected at the outer boundarypoint Sn also proceeds toward the object side of the line 19 n thatconnects the center of curvature 11 to the outer boundary point Sn ofthe field of view in the plane of FIG. 15(a). When the hypotheticallight rays that come from the center Pc of the entrance pupil of theobjective optical system 3 are reflected at the outer boundary points Smand Sn, the reflected image range 15 of the entrance pupil of theobjective optical system 3 (as defined previously) will becomeexcessively large.

FIG. 15(b) illustrates the reflected image range 15 (as defined above)of the entrance pupil of the objective optical system 3 onto the planeQm that contains the light emitting surface(s) of the light source(s)that form the illumination means 13.

FIGS. 16(a) and 16(b) show another exemplary structure of a capsule-typeendoscope according to the present invention so as to clarify thedifferences between the present invention versus prior art capsule-typeendoscopes, with FIG. 16(a) being a cross-section of a front portion ofthe capsule-type endoscope as viewed from the side, and FIG. 16(b) beinga cross-section of a front portion of the capsule-type endoscope asviewed from the front. In FIGS. 16(a) and 16(b), the center of curvature11 of the inner surface 10 of the transparent cover 8 is in a sector(among the four sectors delineated by the intersection of the lines 7 mand 7 n when these lines are extended backward as shown in FIG. 16(b))that contains the optical axis of the objective optical system and is onthe image side of the center Pc of the entrance pupil of the objectiveoptical system 3. Therefore, the line 7 m is on the object side (i.e.,is to the left in FIG. 16(a)) of the line 19 m that connects the centerof curvature 11 to the outer boundary point Sm, and the line 7 n is alsoon the object side of the line 19 n that connects the center ofcurvature 11 to the outer boundary point Sn, where both Sm and Sn are asdefined previously. It is assumed that hypothetical light rays come fromthe center Pc of the entrance pupil of the objective optical system 3and are reflected at the outer boundary points Sm and Sn of the field ofview in the cross-section (depicted in FIG. 16(a)) that contains thevertex St of the inner surface of the transparent cover and the centerPc of the entrance pupil of the objective optical system. The lightreflected at the point Sm proceeds toward the image side (i.e., to theright in FIG. 16(a)) of the line 19 m that connects the center ofcurvature 11 to the outer boundary point Sm. The light reflected at theouter boundary point Sn also proceeds toward the image side of the line19 n that connects the center of curvature 11 to the outer boundarypoint Sn of the field of view in the plane of the figure. When thehypothetical light rays that come from the center Pc of the entrancepupil of the objective optical system 3 are reflected at the outerboundary points Sm and Sn, the reflected image range 15 of the entrancepupil of the objective optical system 3 will become excessively large onthe plane Qm that contains the light-emitting surface(s) of the lightsource(s) that form the illumination means 13 and will overlap with theobjective optical system 3, as shown in FIG. 16(b).

As described above, it is preferred, for a capsule-type endoscopeembodiment in which the inner surface 10 of the transparent cover isspherical, that the center of curvature 11 of the inner surface 10 ofthe transparent cover 8 is in a sector (among the four sectors definedby the lines 7 m and 7 n when these lines are extended backward as shownin FIG. 16(b)) that does not contain the optical axis of the objectiveoptical system.

It is further preferred that the center of curvature 11 of the innersurface 10 of the transparent cover 8 and the center Pc of the entrancepupil of the objective optical system 3 are positioned so as to satisfythe above Condition (1).

When the upper limit of Condition (1) is not satisfied, the objectiveoptical system 3 will be too close to the vertex St of the inner surface10 of the transparent cover 8 and not leave a sufficient space toaccommodate the illumination light source(s) of the illumination means13. When the lower limit of the Condition (1) is not satisfied, theobjective optical system 3 will be too far away from the vertex St ofthe inner surface 10 of the transparent cover 8, thereby increasing theentire capsule length.

FIGS. 13(a) and 13(b) and FIGS. 14(a) and 14(b) show second and thirdpossible modifications to Embodiment 2, with FIGS. 13(a) and 14(a) beingcross sections as viewed from the side, with the plane of thecross-section including the optical axis of the objective optical systemand the vertex St of the inner surface of the transparent cover, andFIGS. 13(b) and 14(b) being cross sections as viewed from the front. Inthe second possible modification shown in FIGS. 13(a) and 13(b), theinner surface 10 of the transparent cover 8 is an aspheric surfacewherein the curvature increases with increasing distance from the vertexSt of the inner surface. In the third possible modification shown inFIGS. 14(a) and 14(b), the inner surface 10 of the transparent cover 8is an aspheric surface wherein the curvature decreases with increasingdistance from the vertex St of the inner surface. When the inner surface10 of the transparent cover 8 is aspheric, the transparent cover 8 andthe objective optical system 3 are positioned as follows: the curvature(curvature is defined as 1 divided by the radius of curvature R at thepoint of interest) at the points Sm and Sn (both as defined previously)is obtained and the centers of curvature OA and OB of spherical surfaceshaving a curvature of 1/R are positioned in a sector (among the foursectors delineated by the lines 7 m and 7 n when these lines areextended backward as shown in FIGS. 13(a) and 14(a)) that does notcontain the optical axis of the objective optical system.

In the second and third possible modifications to the capsule-typeendoscope of Embodiment 2 that are shown in FIGS. 13(a) to 14(b), theobjective optical system 3 is positioned so that the point ofintersection X with the plane Qm of a line drawn from the vertex Stperpendicular to the plane Qm (St and Qm are as defined previously) ison a line that connects the point P and the center 16 of the reflectedimage range 15. In these possible modifications, multiple illuminationlight sources are provided and are positioned outside the reflectedimage range 15. With the second and third possible modifications toEmbodiment 2 shown in FIGS. 13(a) to 14(b), a sufficient space forproviding the image pickup unit 1 while using multiple illuminationlight sources is ensured even if the inner surface 10 of the transparentcover 8 is aspheric. Therefore, a small-sized, capsule-type endoscopecan be provided that prevents illumination light that is reflected bythe inner surface 10 of the transparent cover 8 from causing flare inthe objective optical system 3.

Embodiment 3

FIG. 17 shows a cross-section of a front portion of a capsule-typeendoscope according to Embodiment 3 of the present invention, as viewedfrom the side. More specifically, it illustrates 10 a cross section thatcontains the optical axis 4 of the objective optical system 3 and thevertex St of the inner surface 10 of the transparent cover 8, and showsthe imaging of an object point that is positioned on the outer surface 9of the transparent cover 8 at the outer limits of the field of view ofthe objective optical system 3. The image pickup unit I of thecapsule-type endoscope of Embodiment 3 includes an objective opticalsystem 3 having lens components 5, 5 (which may each consist of a singlelens element), a diaphragm (not shown), a lens frame (not shown), aspacer ring (not shown), an image pickup element 2, and an image pickupelement frame (not shown).

As shown in FIG. 17, the center of the field of view of the objectiveoptical system 3 is positioned off the longitudinal axis of the capsule;thus, the distance between the most object-side surface of the objectiveoptical system 3 and the outer surface 9 of the transparent cover 8varies, depending on the viewing direction. This causes the imageposition for each object point to shift. Therefore, if the image pickupsurface of the image pickup element 2 is positioned orthogonal to theoptical axis as in prior art capsule-type endoscopes, objects that arein contact with the outer surface of the transparent cover 8 at theouter limits of the field of view of the objective optical system 3 willbe partially out of focus, making observations difficult.

Hence, in the endoscope of Embodiment 3 (as shown in FIG. 17), the imagepickup element 2 is tilted so as to be non-orthogonal to the opticalaxis of the objective optical system 3 in such a manner that the imagepickup surface is positioned at the image positions ObA′ and ObB′, whichcorrespond to the distances ObA and ObB between the most object-sidesurface of the objective optical system 3 and the outer surface 9 of thetransparent cover 8 at the outer limits of the field of view of theobjective optical system 3. With a capsule-type endoscope having such astructure, focal shifts on the image plane caused by differences inobject point distances to the outer surface 9 of the transparent cover 8in different viewing directions can be corrected, and a small-sized,capsule-type endoscope that allows for clear observation of objects thatare in contact with the outer surface 9 of the transparent cover 8 canbe realized.

When it is difficult to tilt the image pickup element 2 in a manner suchthat the image-forming points at the image positions ObA and ObBcompletely coincide with the image pickup surface, the tilt of the imagepickup element 2 can be adjusted relative to the optical axis of theobjective optical system 3 in such a manner that the diameter of a lightflux on the image pickup surface extends over approximately four pixelsfor any viewing direction, as this yields images that are practically infocus.

Embodiment 4

FIG. 18 shows the front portion of a capsule-type endoscope according toEmbodiment 4 of the present invention and is for explaining theimage-formation of an object point on the outer surface 9 of thetransparent cover 8 at the outer limits of the field of view of theobjective optical system 3 for this embodiment. The plane of the figureis a cross-section that contains the optical axis 4 of the objectiveoptical system 3 and the vertex St of the inner surface 10 of thetransparent cover 8. The capsule-type endoscope of Embodiment 4 isdifferent from that of Embodiment 3 in that focal shifts on the imageplane caused by differences in the object point distances as measuredfrom the outer surface 9 of the transparent cover 8 in different viewingdirections are corrected without having to tilt the image pickupelement. In this embodiment, the center of the field of view of theobjective optical system 3 is positioned off the longitudinal axis ofthe capsule. In the capsule-type endoscope of Embodiment 4, the outersurface 9 of the transparent cover 8 is approximately symmetricallysituated about the optical axis 4 of the objective optical system 3, andthe vertex St of the inner surface of the transparent cover is offsetfrom the optical axis 4 of the objective optical system 3. Moreover, theouter surface 9 of the transparent cover 8 is spherical in shape. Thedistance between the center of curvature 12 of the outer surface 9 ofthe transparent cover 8 and the optical axis 4 of the objective opticalsystem is 0.4 mm. With this structure, focal shifts on the image planecaused by differences in the object point distance when the object pointis positioned on the outer surface 9 of the transparent cover 8 indifferent viewing directions are not significant and can be correctedwithout having to tilt the image pickup element.

Embodiment 5

FIGS. 19(a) and 19(b) show the front portion of a capsule-type endoscopeaccording to Embodiment 5 of the present invention, with FIG. 19(a)being a cross section (of a front portion of the capsule-shapedendoscope as viewed from the side) that contains the optical axis 4 ofthe objective optical system 3 and the vertex St of the inner surface 10of the transparent cover 8, and FIG. 19(b) being a cross-section of afront portion of the capsule-shaped endoscope as viewed from the front.FIG. 19(a) illustrates forming images of object points on the outersurface 9 of the transparent cover 8 at the outer limits of the field ofview of the objective optical system 3. FIG. 19(b) shows the positionalrelationships, within a plane Qm that contains the light emittingsurface(s) of the illumination light source(s) that form an illuminationmeans, of the centers of curvature 11 and 12 of the inner and outersurfaces 10 and 9, respectively, of the transparent cover 8 and thereflected image range 15 (as defined previously) of the entrance pupilof the objective optical system. In the capsule-type endoscope ofEmbodiment 5, the center of curvature 12 of the outer surface 9 of thetransparent cover 8 (which lies on the longitudinal axis of the capsule)is offset relative the optical axis 4 of the objective optical system,as well as relative to the center of curvature 11 of the inner surface10 of the transparent cover 8, and one of the optical elements 5, 5forming the objective optical system 3 is de-centered in order tocompensate for object points at the outer surface of the transparentcover in different viewing directions being at different objectdistances from the entrance pupil of the objective optical system. Thus,focal shifts on the image plane caused by differences in the objectpoint distances to the outer surface 9 of the transparent cover 8 indifferent viewing directions can be corrected even if the center of thefield of view of the objective optical system 3 is positioned away fromthe longitudinal axis of the capsule.

Embodiment 6

FIGS. 20(a) and 20(b) show cross sections of the front portion of acapsule-type endoscope according to Embodiment 6 of the presentinvention, with FIG. 20(a) illustrating a cross section that containsthe optical axis 4 of the objective optical system 3 and the vertex Stof the inner surface 10 of the transparent cover 8 as viewed from theside, and FIG. 20(b) illustrating a cross-section as viewed from thefront. FIG. 20(a) illustrates forming images of object points on theouter surface 9 of the transparent cover 8 at the outer limits of thefield of view of the objective optical system 3. FIG. 20(b) shows thepositional relationships, within a plane Qm that contains the lightemitting surfaces of the light sources that form the illumination means13, of the centers of curvature 11 and 12 of the inner and outersurfaces 10 and 9, respectively, of the transparent cover 8 and thereflected image range 15 (as defined previously) of the entrance pupilof the objective optical system.

The inner surface 10 of the transparent cover 8 of Embodiment 6 isspherical. The center of curvature 11 of the inner surface 10 of thetransparent cover 8 is on a line 17 that passes through the center Pc ofthe entrance pupil of the objective optical system 3 and is orthogonalto the optical axis 4 of the objective optical system 3. The entrancepupil of the objective optical system 3 coincides with the mostobject-side surface of the lenses 5, 5 that form the objective opticalsystem 3. The objective optical system 3 is positioned so that theentrance pupil plane thereof is in the same plane as the plane Qm thatcontains the light emitting surfaces 14 of the illumination lightsources that form the illumination means 13.

In order to provide uniform illumination within the field of view of theobjective optical system 3 in the present invention, the illuminationlight sources that form the illumination means 13 are evenly positionedaround the optical axis of the objective optical system. Preferably, thefollowing Condition (7) is satisfied:PX>(φL/2)+(ΔD)   Condition (7)where

PX is the distance, on the plane Qm, between the intersection points Pand X, where P is the intersection with the plane Qm of the optical axisof the objective optical system, and X is the intersection with theplane Qm of a line drawn from the vertex St of the inner surface of thetransparent cover that is perpendicular to the plane Qm;

φL is the outer diameter of the most object-side lens component of theobjective optical system; and

ΔD is the smallest distance between the center of an illumination lightsource and its outer periphery.

In the capsule-type endoscope of Embodiment 6, φL=0.75 mm and ΔD=0.55mm; therefore the distance between the intersection points P and X is1.65 mm. This embodiment realizes a small-sized, capsule-type endoscopedespite there being multiple illumination light sources that form theillumination means 13 so as to assure a sufficient brightness ofillumination while simultaneously preventing light emitted from anillumination light source and reflected by the inner surface 10 of thetransparent cover 8 from entering the entrance pupil of the objectiveoptical system 3, thereby preventing flare.

Embodiment 7

FIGS. 21(a) and 21(b) show cross sections of the front portion of acapsule-type endoscope according to Embodiment 7 of the presentinvention, with FIG. 21(a) illustrating a cross section that containsthe optical axis 4 of the objective optical system 3 and the vertex Stof the inner surface 10 of the transparent cover 8 as viewed from theside, and FIG. 21(b) illustrating a cross-section as viewed from thefront. FIG. 21(a) illustrates forming images of object points on theouter surface 9 of the transparent cover 8 at the outer limits of thefield of view of the objective optical system 3. FIG. 21(b) shows thepositional relationships, within the plane Qm that contains the lightemitting surfaces of the illumination light sources that form theillumination means, among the points St, Pc and P′c and the reflectedimage range 15 (all as defined previously) of the entrance pupil of theobjective optical system.

The inner and outer surfaces 10 and 9 of the transparent cover 8 in thecapsule-type endoscope of Embodiment 7 are both ellipsoidal. The innersurface 10 is defined by the following equation:(x ²/4.96²)+(y ²/5.55²)=1   Equation (B)where x and y are the coordinates of the inner surface.

The coordinates of the focal points (0, ±2.48) of the ellipsoidaltransparent cover 8 are provided such that the center 11 of the innersurface 10 is the origin. The center 11 of the inner surface 10 is thecenter of the ellipsoid and is positioned at the intersection of themajor and minor axes of the ellipsoid.

With the structure above, the reflected image range 15 of the entrancepupil of the objective optical system 3 projected via the inner surface10 of the transparent cover 8 is as shown in FIG. 21(b). Three LEDs,that each comprise an illumination source of the illumination means 13,are positioned around the optical axis of the objective optical system 3outside the reflected image range 15 (as defined previously). The center16 of the reflected image range 15 is positioned along a line 17 in theplane Qm that connects the points P(Pc) and X, where P and X are asdefined above. With the capsule-type endoscope of Embodiment 7, theouter diameter of the capsule can be reduced from 12 mm, as in a priorart capsule-type endoscope, to 10.85 mm (as shown by the hatched area inFIG. 21(b)).

As is apparent from the endoscope of Embodiment 7, the capsule-typeendoscope of the present invention prevents light that is emitted by theillumination means 13 and reflected by the inner surface 10 of thetransparent cover 8 from reaching the entrance pupil of the objectiveoptical system 3, thus preventing flare even though the inner surface 10of the transparent cover 8 is ellipsoidal in shape, while providing asmall-sized, capsule-type endoscope that provides clear images.

When the inner surface 10 of the transparent cover 8 is ellipsoidal inshape, a coordinate system can be established with the origin at thecenter Pc of the entrance pupil of the objective optical system 3, withthe y-axis being along the line that connects the center Pc of theentrance pupil of the objective optical system and the center ofcurvature 11 of the inner surface 10 of the transparent cover 8, and thex-axis being along the line that passes through the center Pc of theentrance pupil of the objective optical system 3 and is orthogonal tothe y-axis. The positive direction of the y-axis is in the directionfrom the origin to the center of curvature 11 of the inner surface 10 ofthe transparent cover 8. Then, primary light 7 around the outermostperipheries of the field of view will be reflected by the inner surface10 of the transparent cover 8 and will reach the x-y plane, with they-coordinate being positive when the following Condition (8) issatisfied:D 1>(β1)2/(4·α1)   Condition (8)where

β1 equals the minor diameter of the ellipsoid divided by 2, and

α1 equals the major diameter of the ellipsoid divided by 2.

Therefore, if the center coordinates of the light emitting surfaces ofthe illumination means 13 have y>0 on the x-y plane, light emitted fromthe illumination light sources of the illumination means 13 andreflected by the inner surface 10 of the transparent cover 8 will notenter the entrance pupil of the objective optical system 3, therebypreventing flare.

FIG. 24 is an illustration to explain a capsule-type endoscope system inwhich a marking can be displayed by analyzing the position where the tipof the puncture needle makes contact with a living tissue surface, basedon the positional relationship between the puncture needle projectionport, the living tissue, and the moving direction of the punctureneedle.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention. Rather, the scopeof the invention shall be defined as set forth in the following claimsand their legal equivalents. All such modifications as would be obviousto one skilled in the art are intended to be included within the scopeof the following claims.

1. A capsule-type endoscope comprising: a capsule; an image pickup unitthat includes an objective optical system having an optical axis and afield of view, and an image pickup element; an illumination light sourcehaving a light emitting surface; and a transparent cover that seals theobjective optical system, the image pickup unit, and the illuminationlight source within the capsule; wherein an inner surface of thetransparent cover is spherical within the field of view of the objectiveoptical system so as to have a center of curvature, the center ofcurvature is offset from the optical axis of the objective opticalsystem, and the following condition is satisfied:0.01<L 1/R tan θ<0.5 where L1 is the distance between the center ofcurvature of the inner surface of the transparent cover and the opticalaxis of the objective optical system; R is the radius of curvature ofthe inner surface of the transparent cover; and θ is the half-fieldangle of the objective optical system.
 2. The capsule-type endoscopeaccording to claim 1, wherein the light emitting surface of theillumination light source, which is planer, is positioned in such amanner that it does not overlap any part of an image of the entrancepupil of the objective optical system, said image being defined whenhypothetical light rays emitted from the center of the entrance pupil atthe outer limits of the field of view of the objective optical systemare projected onto a plane Qm by being reflected by the inner surface ofthe transparent cover, where the plane Qm is the plane containing thelight emitting surface of the illumination light source.
 3. Thecapsule-type endoscope according to claim 1, and further comprising: atank that is located within the capsule; and a nozzle, that is locatedoutside the capsule, for spraying a substance carried in the tank;wherein the nozzle is located at a position and orientation that isoutside the field of view of the objective optical system, but the fieldof view of the objective optical system and a spray range of the nozzleoverlap.
 4. The capsule-type endoscope according to claim 1, and furthercomprising: a puncture needle; a projection port for the punctureneedle; and a mechanism that is located inside the capsule for pushingthe puncture needle through the projection port; wherein the projectionport is located at a position that is outside the field of view of theobjective optical system; and when the puncture needle is pushed throughthe projection port, a tip of the puncture needle enters within thefield of view of the objective optical system prior to the punctureneedle making contact with a puncture target region.
 5. The capsule-typeendoscope according to claim 1, and further comprising: a tank that islocated within the capsule; and a nozzle, that is located outside thecapsule, for spraying a substance carried in the tank; wherein at leasta portion of the nozzle is positioned within the field of view of theobjective optical system.
 6. The capsule-type endoscope according toclaim 1, wherein the objective optical system satisfies the followingconditions: R1≧5 lines per mm R2≧1 line per mm where R1 is theresolution on the optical axis at positions between the most object-sidesurface of the objective optical system and the point of intersection ofthe optical axis of the objective optical system with an outer surfaceof the transparent cover; and R2 is the resolution on the optical axisat positions between the most object-side surface of the objectiveoptical system and a far point of the depth of field of the objectiveoptical system.
 7. The capsule-type endoscope according to claim 2,wherein: at least one optical component of the image pickup unit isde-centered relative to other components of the image pickup unit. 8.The capsule-type endoscope according to claim 2, wherein an outersurface of the transparent cover is spherical and within 0.4 mm of beingsymmetric about the optical axis of the objective optical system.
 9. Thecapsule-type endoscope according to claim 3, wherein the nozzle isoriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and a centerline of an orifice of the nozzle.
 10. Thecapsule-type endoscope according to claim 3, wherein: the nozzle isconnected to the tank through the transparent cover at a location thatis outside the field of view of the objective optical system.
 11. Thecapsule-type endoscope according to claim 3, wherein the nozzle and thetank are detachably attached to the capsule.
 12. The capsule-typeendoscope according to claim 4, wherein the projection port passesthrough the transparent cover at a position that is outside the field ofview of the objective optical system.
 13. The capsule-type endoscopeaccording to claim 4, wherein a puncture-needle storage part thatincludes the projection port is detachably attached to the capsule. 14.The capsule-type endoscope according to claim 5, wherein the nozzle isoriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 15. Thecapsule-type endoscope according to claim 5, wherein the nozzle isconnected to the tank through the transparent cover at a location wherethe nozzle is outside the field of view of the objective optical system.16. The capsule-type endoscope according to claim 5, wherein the nozzleand the tank are detachably attached to the capsule.
 17. Thecapsule-type endoscope according to claim 6, wherein the image pickupunit satisfies the following conditions:80<IH/P<50080<FL/P<500400<Fno/P<3000 where IH is the distance, in mm, between the center andthe furthermost point of the effective image pickup area of the lightreceiving surface of the image pickup element; P is the horizontal pixelpitch, in mm, of the image pickup element; FL is the focal length, inmm, of the objective optical system; and Fno is the effective F-numberof the objective optical system.
 18. A capsule-type endoscope having acapsule-shaped exterior surface, said capsule-type endoscope comprising:an image pickup unit that includes an objective optical system and animage pickup element; at least one illumination means; and a transparentcover for covering the image pickup unit and the illumination means;wherein the objective optical system is provided in a manner such thatits optical axis is not orthogonal to the inner surface of thetransparent cover, and at least one of the components of the imagepickup unit is tilted so as to be non-orthogonal to the optical axis ofthe objective optical system or is de-centered relative to othercomponents of the image pickup unit.
 19. The capsule-type endoscopeaccording to claim 18, and further comprising: a tank that is locatedinside the capsule-shaped exterior surface; and a nozzle that is locatedoutside the capsule-shaped exterior surface, said nozzle having a sprayrange for spraying a substance carried within the tank; wherein thenozzle is located at a position and orientation such that the nozzle isoutside the field of view of the objective optical system, but the fieldof view of the objective optical system and the spray range of thenozzle overlap.
 20. The capsule-type endoscope according to claim 18,wherein: a puncture needle and a mechanism, for pushing at least aportion of the puncture needle outside the capsule-shaped exteriorsurface, is located inside the capsule-shaped exterior surface; aprojection port, for the projection of the puncture needle outside thecapsule-shaped exterior surface, is provided on the capsule-shapedexterior surface; and the projection port is provided at a position thatis outside the field of view of the objective optical system and a tipof the puncture needle, when projected through the projection port butbefore making contact with a puncture target region, comes within thefield of view of the objective optical system.
 21. The capsule-typeendoscope according to claim 18, wherein: a tank is provided inside thecapsule-shaped exterior surface; a nozzle, for spraying a substancecarried within the tank, is provided outside the capsule-shaped exteriorsurface; and at least a portion of the nozzle is positioned within thefield of view of the objective optical system.
 22. The capsule-typeendoscope according to claim 19, wherein the nozzle is oriented so thatthe following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 23. Thecapsule-type endoscope according to claim 19, wherein the nozzle isconnected to the tank through the transparent cover at location suchthat the nozzle is outside the field of view of the objective opticalsystem.
 24. The capsule-type endoscope according to claim 19, whereinthe nozzle and the tank are detachably attached to the capsule.
 25. Thecapsule-type endoscope according to claim 20, wherein the projectionport passes through the transparent cover at a location that is outsidethe field of view of the objective optical system.
 26. The capsule-typeendoscope according to claim 20, wherein a puncture-needle storage partthat includes the projection port is detachably attached to the capsule.27. The capsule-type endoscope according to claim 21, wherein the nozzleis provided at an orientation so that the following condition issatisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 28. Thecapsule-type endoscope according to claim 21, wherein the nozzle isconnected to the tank through the transparent cover at a location suchthat the nozzle is outside the field of view of the objective opticalsystem.
 29. The capsule-type endoscope according to claim 21, whereinthe nozzle and the tank are detachably attached to the capsule.
 30. Acapsule-type endoscope that includes, at different positions within acapsule having a transparent cover on the object side of the capsulethat seals the capsule: an objective optical system; an image pickupelement; and an illumination light source; wherein among the foursectors delineated by the intersection of extended lines that connectthe center of the entrance pupil of the objective optical system topoints on the inner surface of the transparent cover that define theouter limits of the field of view of the objective optical system in across section that contains the optical axis of the objective opticalsystem and the vertex of the inner surface of the transparent cover, thecenter of curvature of the inner surface of the transparent cover ispresent in a sector that does not include the optical axis of theobjective optical system.
 31. The capsule-type endoscope according toclaim 30, wherein at least one optical component of the image pickupunit is de-centered relative to other components of the image pickupunit.
 32. The capsule-type endoscope according to claim 30, wherein theouter surface of the transparent cover is spherical and within 0.4 mm ofbeing symmetric about the optical axis of the objective optical system.33. The capsule-type endoscope according to claim 30, wherein: a tank isfurther provided inside the capsule; a nozzle, for spraying a substancecarried in the tank, is provided outside the capsule; and the nozzle islocated at a position that is outside the field of view of the objectiveoptical system, but the field of view of the objective optical systemand a spray range of the nozzle overlap.
 34. The capsule-type endoscopeaccording to claim 30, wherein: a puncture needle and a mechanism forpushing the puncture needle outside the capsule are further providedinside the capsule; a projection port for the puncture needle isprovided on the exterior surface of the capsule; and the projection portis provided at a position that is outside the field of view of theobjective optical system, but when the puncture needle is projectedthrough the projection port, a tip of the puncture needle comes withinthe field of view of the objective optical system before the punctureneedle makes contact with a puncture target region.
 35. The capsule-typeendoscope according to claim 30, wherein: a tank is further providedinside the capsule; a nozzle, for spraying a substance carried in thetank, is provided outside the capsule; and at least a portion of thenozzle is located within the field of view of the objective opticalsystem.
 36. The capsule-type endoscope according to claim 30, wherein aninner surface of the transparent cover is an aspheric surface with acurvature that decreases with increasing distance from the vertex of theinner surface.
 37. The capsule-type endoscope according to claim 30,wherein an inner surface of the transparent cover is an aspheric surfacewith a curvature that increases with increasing distance from the vertexof the inner surface.
 38. The capsule-type endoscope according to claim30, wherein the objective optical system satisfies the followingconditions: R1≧5 lines per mm R2≧1 line per mm where R1 is theresolution on the optical axis at positions between the most object-sidesurface of the objective optical system and the point of intersection ofthe optical axis of the objective optical system with an outer surfaceof the transparent cover; and R2 is the resolution on the optical axisat positions between the most object-side surface of the objectiveoptical system and a far point of the depth of field of the objectiveoptical system.
 39. The capsule-type endoscope according to claim 33,wherein the nozzle is oriented so that the following condition issatisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 40. Thecapsule-type endoscope according to claim 33, wherein the nozzle isconnected to the tank through the transparent cover at a location suchthat the nozzle is outside the field of view of the objective opticalsystem.
 41. The capsule-type endoscope according to claim 33, whereinthe nozzle and the tank are detachably attached to the capsule.
 42. Thecapsule-type endoscope according to claim 34, wherein the projectionport passes through the transparent cover at a location that is outsidethe field of view of the objective optical system.
 43. The capsule-typeendoscope according to claim 34, wherein a puncture-needle storage partthat includes the projection port is detachably attached to the capsule.44. The capsule-type endoscope according to claim 35, wherein the nozzleis oriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 45. Thecapsule-type endoscope according to claim 35, wherein the nozzle isconnected to the tank through the transparent cover at a location suchthat the nozzle is outside the field of view of the objective opticalsystem.
 46. The capsule-type endoscope according to claim 35, whereinthe nozzle and the tank are detachably attached to the capsule.
 47. Thecapsule-type endoscope according to claim 38, wherein the image pickupunit satisfies the following conditions:80<IH/P<50080<FL/P<500400<Fno/P<3000 where IH is the distance, in mm, between the center andthe furthermost point of the effective image pickup area of thelight-receiving surface of the image pickup element; P is the horizontalpixel pitch, in mm, of the image pickup element; FL is the focal length,in mm, of the objective optical system; and Fno is the effectiveF-number of the objective optical system.
 48. A capsule-type endoscopethat includes an image pickup unit comprising an objective opticalsystem, an image pickup element, and at least one illumination lightsource located at different positions within a capsule that has atransparent cover that seals these items within the capsule, wherein atleast within the field of view of the objective optical system, theinner surface of the transparent cover is spherical; light-emittingsurface(s) of the illumination light source(s) does(do) not overlap withan image of the entrance pupil of the objective optical system that isprojected onto a plane Qm by light rays that are reflected by the innersurface of the transparent cover; and X lies on a line drawn from P toP′where Qm is a plane that contains the light-emitting surface(s) of theillumination light source(s); X is the point of intersection with theplane Qm of a line drawn from the vertex St of the inner surface of thetransparent cover so as to be normal to the plane Qm; P is the point ofintersection with the plane Qm of a line that is drawn from the centerof the entrance pupil of the objective optical system so as to beperpendicular to the plane Qm; and P′ is the point of intersection withthe plane Qm of a line that is drawn from a point P′c so as to be normalto the plane Qm; and P′c is the point of intersection of hypotheticallight rays emitted from the center of the entrance pupil of theobjective optical system after such light rays are reflected by theinner surface of the transparent cover at positions that are at theouter limits of the field of view of the objective optical system in across section that contains the vertex of the inner surface of thetransparent cover and the optical axis of the objective optical system.49. The capsule-type endoscope according to claim 48, wherein at leastone of the components of the image pickup unit is tilted so as to benon-orthogonal to the optical axis of the objective optical system or isde-centered relative to other components of the image pickup unit. 50.The capsule-type endoscope according to claim 48 wherein: the outersurface of the transparent cover is spherical and within 0.4 mm of beingsymmetric about the optical axis of the objective optical system. 51.The capsule-type endoscope according to claim 48, wherein: a tank isfurther provided inside the capsule; a nozzle, for spraying a substancecarried in the tank, is provided outside the capsule; and the nozzle isprovided at a position that is outside the field of view of theobjective optical system but where the field of view of the objectiveoptical system and a spray range of the nozzle overlap.
 52. Thecapsule-type endoscope according to claim 48, wherein: a puncture needleand a mechanism for pushing the puncture needle outside the capsule arefurther provided inside the capsule; a projection port for the punctureneedle is provided on an exterior surface of the capsule; and theprojection port is located at a position that is outside the field ofview of the objective optical system but, when the puncture needle isprojected through the projection port, the tip of the puncture needlecomes within the field of view of the objective optical system before itmakes contact with a puncture target region.
 53. The capsule-typeendoscope according to claim 48, wherein: a tank is further providedinside the capsule; a nozzle, for spraying a substance carried in thetank, is provided outside the capsule; and at least a portion of thenozzle is positioned within the field of view of the objective opticalsystem.
 54. The capsule-type endoscope according to claim 48, whereinthe objective optical system satisfies the following conditions: R1≧5lines per mm R2≧1 line per mm where R1 is the resolution on the opticalaxis at positions between the most object-side surface of the objectiveoptical system and the point of intersection of the optical axis of theobjective optical system with an outer surface of the transparent cover;and R2 is the resolution on the optical axis at positions between themost object-side surface of the objective optical system and a far pointof the depth of field of the objective optical system.
 55. Thecapsule-type endoscope according to claim 51, wherein the nozzle isoriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 56. Thecapsule-type endoscope according to claim 51, wherein the nozzle isconnected to the tank through the transparent cover at a location thatis outside the field of view of the objective optical system.
 57. Thecapsule-type endoscope according to claim 51, wherein the nozzle and thetank are detachably attached to the capsule.
 58. The capsule-typeendoscope according to claim 52, wherein the projection port passesthrough the transparent cover at a location that is outside the field ofview of the objective optical system.
 59. The capsule-type endoscopeaccording to claim 52, wherein a puncture-needle storage part thatincludes the projection port is detachably attached to the capsule. 60.The capsule-type endoscope according to claim 53, wherein the nozzle isoriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 61. Thecapsule-type endoscope according to claim 53, wherein the nozzle isconnected to the tank through the transparent cover at a location suchthat the nozzle is outside the field of view of the objective opticalsystem.
 62. The capsule-type endoscope according to claim 53, whereinthe nozzle and the tank are detachably attached to the capsule.
 63. Thecapsule-type endoscope according to claim 54, wherein the image pickupunit satisfies the following conditions:80<IH/P<50080<FL/P<500400<Fno/P<3000 where IH is the distance, in mm, between the center andthe furthermost point of the effective image pickup area of thelight-receiving surface of the image pickup element; P is the horizontalpixel pitch, in mm, of the image pickup element; FL is the focal length,in mm, of the objective optical system; and Fno is the effectiveF-number of the objective optical system.
 64. A capsule-type endoscopecomprising: an image pickup unit that includes an objective opticalsystem having an optical axis and an image pickup element; at least oneillumination means; and a transparent cover, wherein the objectiveoptical system is provided in a manner such that its optical axis is notorthogonal to an inner surface of the transparent cover; and at leastone optical member within the objective optical system is de-centeredrelative to other optical members within the objective optical system orthe image pickup surface of the image pickup element is tilted so as tobe non-orthogonal to the optical axis of the objective optical system.65. The capsule-type endoscope according to claim 64, wherein an outersurface of the transparent cover is spherical and within 0.4 mm of beingsymmetric about the optical axis of the objective optical system. 66.The capsule-type endoscope according to claim 64, wherein an image of anentrance pupil of the objective optical system that is projected onto aplane Qm by light rays that are reflected by the inner surface of thetransparent cover and the light emitting surface of the at least oneillumination means do not overlap, where the plane Qm is the planecontaining the light emitting surface of the illumination means.
 67. Thecapsule-type endoscope according to claim 64, and further comprising: atank that is positioned inside the capsule; a nozzle, for spraying asubstance carried in the tank, is provided outside the capsule; and thenozzle is provided at a location that is outside a field of view of theobjective optical system but where the field of view of the objectiveoptical system and a spray range of the nozzle overlap.
 68. Thecapsule-type endoscope according to claim 64, and further comprising: apuncture needle and a mechanism for pushing the puncture needle outsidethe capsule are further provided inside the capsule; a projection portfor the puncture needle is provided on an exterior surface of thecapsule-type endoscope; and the projection port is provided at aposition that is outside a field of view of the objective opticalsystem, but when the puncture needle is projected through the projectionport, a tip of the puncture needle comes within the field of view of theobjective optical system before it makes contact with a puncture targetregion.
 69. The capsule-type endoscope according to claim 64, andfurther comprising: a tank that is located within an exterior surface ofthe capsule-type endoscope; a nozzle, for spraying a substance carriedin the tank, is located outside the exterior surface of the capsule-typeendoscope; and at least a portion of the nozzle is positioned within afield of view of the objective optical system.
 70. The capsule-typeendoscope according to claim 67, wherein the nozzle is oriented so thatthe following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 71. Thecapsule-type endoscope according to claim 67, wherein the nozzle isconnected to the tank through the transparent cover at a location thatis outside the field of view of the objective optical system.
 72. Thecapsule-type endoscope according to claim 67, wherein the nozzle and thetank are detachably attached to the capsule.
 73. The capsule-typeendoscope according to claim 68, wherein the projection port passesthrough the transparent cover at a location that is outside the field ofview of the objective optical system.
 74. The capsule-type endoscopeaccording to claim 68, wherein a puncture-needle storage part thatincludes the projection port is detachably attached to the capsule. 75.The capsule-type endoscope according to claim 69, wherein the nozzle isoriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 76. Thecapsule-type endoscope according to claim 69, wherein the nozzle isconnected to the tank through the transparent cover at a location thatis outside the field of view of the objective optical system.
 77. Thecapsule-type endoscope according to claim 69, wherein the nozzle and thetank are detachably attached to the capsule.
 78. A capsule-typeendoscope comprising: an image pickup unit that includes an objectiveoptical system and an image pickup element; at least one illuminationmeans; and a transparent cover; wherein an inner surface of thetransparent cover has an ellipsoidal shape and, in a cross section thatcontains the optical axis of the objective optical system and the vertexof the inner surface of the transparent cover, D1 is greater than(β1)²/(4·α1), where β1 equals the minor diameter of the ellipsoiddivided by 2, and α1 equals the major diameter of the ellipsoid dividedby
 2. 79. The capsule-type endoscope according to claim 78, wherein: thelight emitting surface of the illumination light source does not overlapan image of the entrance pupil of the objective optical system that isformed by light rays that are projected onto a plane Qm by beingreflected from the inner surface of the transparent cover, where theplane Qm is the plane containing the light emitting surface of theillumination light source.
 80. The capsule-type endoscope according toclaim 78, and further comprising: a tank that is located within anexterior surface of the capsule-type endoscope; and a nozzle, forspraying a substance carried in the tank, that is located outside theexterior surface of the capsule-type endoscope; wherein the nozzle ispositioned outside a field of view of the objective optical system, butwhere the field of view of the objective optical system and a sprayrange of the nozzle overlap.
 81. The capsule-type endoscope according toclaim 78, wherein: a puncture needle and a mechanism for pushing thepuncture needle outside an exterior surface of the capsule-typeendoscope are further provided inside said exterior surface; aprojection port for the puncture needle is provided on said exteriorsurface of the capsule; and the projection port is provided at aposition that is outside a field of view of the objective opticalsystem, but when the puncture needle is projected through the projectionport a tip of the puncture needle will come within the field of view ofthe objective optical system before it makes contact with a puncturetarget region.
 82. The capsule-type endoscope according to claim 78, andfurther comprising: a tank that is located within an exterior surface ofthe capsule-type endoscope; and a nozzle, for spraying a substancecarried in the tank, that is located outside the exterior surface of thecapsule-type endoscope; wherein at least a portion of the nozzle ispositioned within a field of view of the objective optical system. 83.The capsule-type endoscope according to claim 78, wherein the objectiveoptical system satisfies the following conditions: R1≧5 lines per mmR2≧1 line per mm where R1 is the resolution on the optical axis atpositions between the most object-side surface of the objective opticalsystem and the point of intersection of the optical axis of theobjective optical system with an outer surface of the transparent cover;and R2 is the resolution on the optical axis at positions between themost object-side surface of the objective optical system and a far pointof the depth of field of the objective optical system.
 84. Thecapsule-type endoscope according to claim 78, wherein at least one ofthe components of the image pickup unit is tilted so as to benon-orthogonal to the optical axis of the objective optical system or isde-centered relative to other components of the image pickup unit. 85.The capsule-type endoscope according to claim 78, wherein an outersurface of the transparent cover is spherical and within 0.4 mm of beingsymmetric about the optical axis of the objective optical system. 86.The capsule-type endoscope according to claim 80, wherein the nozzle isoriented such that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 87. Thecapsule-type endoscope according to claim 80, wherein the nozzle isconnected to the tank through the transparent cover at a location thatis outside a field of view of the objective optical system.
 88. Thecapsule-type endoscope according to claim 80, wherein the nozzle and thetank are detachably attached to the capsule.
 89. The capsule-typeendoscope according to claim 81, wherein the projection port passesthrough the transparent cover at a location that is outside the field ofview of the objective optical system.
 90. The capsule-type endoscopeaccording to claim 81, wherein a puncture-needle storage part thatincludes the projection port is detachably attached to the capsule. 91.The capsule-type endoscope according to claim 82, wherein the nozzle isoriented such that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 92. Thecapsule-type endoscope according to claim 82, wherein the nozzle isconnected to the tank through the transparent cover at a location thatis outside the field of view of the objective optical system.
 93. Thecapsule-type endoscope according to claim 82, wherein the nozzle and thetank are detachably attached to the capsule.
 94. The capsule-typeendoscope according to claim 83, wherein the image pickup unit satisfiesthe following conditions:80<IH/P<50080<FL/P<500400<Fno/P<3000 where IH is the distance, in mm, between the center andthe furthermost point of the effective image pickup area of thelight-receiving surface of the image pickup element; P is the horizontalpixel pitch, in mm, of the image pickup element; FL is the focal length,in mm, of the objective optical system; and Fno is the effectiveF-number of the objective optical system.
 95. A capsule-type endoscopesystem comprising: a capsule-type endoscope that includes a light sourcefor providing illumination inside a living body, an image pickup unitfor capturing images inside the body, a spray unit for spraying asubstance inside the body, and a communication unit for transmittingimage signals to outside the body, and for receiving signals forcontrolling the spray unit from outside the body; a communicationdevice, external of the body, for communicating with the capsule-typeendoscope; and a personal computer, external of the body, that includesa memory for storing image signals received from the capsule-typeendoscope, an image processing circuit for processing image signals andfor generating images, and a control circuit for controlling the timingof spraying by the spray unit; wherein the spray unit includes a tankthat is located inside an exterior surface of the capsule-type endoscopeand a spray nozzle that is located outside the exterior surface of thecapsule-type endoscope.
 96. The capsule-type endoscope system accordingto claim 95, and further comprising: an orientation control device forcontrolling, from outside the body, the orientation of the capsule-typeendoscope when the capsule-type endoscope is inside the body; whereinsaid control circuit also has a function to control the orientation ofthe capsule-type endoscope.
 97. The capsule-type endoscope systemaccording to claim 95, wherein: the control circuit of the personalcomputer has a function to automatically control the orientation of thecapsule-type endoscope for directing the orifice of the spray unit tospray a target.
 98. The capsule-type endoscope system according to claim95, and further comprising: a display device for displaying imagesprocessed by the personal computer is provided; wherein the imageprocessing circuit of the personal computer has a function to display asymbol mark at the intersection of the centerline of an orifice of thespray unit with the image of an in vivo object displayed on the displaydevice.
 99. The capsule-type endoscope system according to claim 95,wherein: the image processing circuit of the personal computer has afunction of performing an analysis of the morphology and color tone ofan object captured in the image; and a screening, for particular lesionpatterns stored in the memory of the personal computer, is concurrentlyperformed with the image processing.
 100. A capsule-type endoscopesystem comprising: a capsule-type endoscope that includes a light sourcefor providing illumination inside a living body, an image pickup unitfor capturing images inside the body, a puncture needle unit forinserting a needle into tissue of the body so as to deliver a substanceor to collect a sample of the tissue, and a communication unit fortransmitting image signals outside the living body and for receivingsignals for controlling the puncture needle unit from outside the livingbody; a communication device external of the living body forcommunicating with the capsule-type endoscope; and a personal computerexternal of the living body and equipped with a memory for storing imagesignals from the capsule-type endoscope, an image processing circuit forprocessing image signals and for generating images, and a controlcircuit for controlling the timing of insertion of the puncture needleinto the tissue.
 101. The capsule-type endoscope system according toclaim 100, and further comprising: an orientation control device forexternally controlling the orientation of the capsule-type endoscopeinside the living body; wherein the control circuit of the personalcomputer has a function to control the orientation of the capsule-typeendoscope.
 102. The capsule-type endoscope system according to claim100, and further comprising: a display device for displaying imagesprocessed by the personal computer; wherein the image processing circuitof the personal computer can perform an analysis of the distance thatthe puncture needle has been inserted in the living tissue after a tipof the puncture needle makes contact with the surface of the livingtissue and can display the result of the analysis, as well as an imageof the surface of the living tissue, on the display screen of thedisplay device.
 103. The capsule-type endoscope system according toclaim 100, and further comprising: a display device for displayingimages processed by the personal computer; wherein the image processingcircuit of the personal computer can perform an analysis, before theneedle makes contact, of the point where the tip of the needle will makecontact with a surface of the tissue, based on the positionalrelationship between the projection port, the surface of the tissue, andthe moving direction of the puncture needle and can display an image ofthe surface of the tissue as well as a pointer, such as an arrow,superimposed on the image.
 104. An observation method using acapsule-type endoscope system, said system comprising: a capsule-typeendoscope that includes a light source for providing illumination insidea living body, an image pickup unit for capturing images inside thebody, a spray unit for spraying a substance inside the body, and acommunication unit for transmitting image signals taken inside the bodyto outside the body and for receiving signals that control the sprayunit from outside the body; an orientation control device, external ofthe body, for controlling the orientation of the capsule-type endoscopeinside the body; a communication device, external of the body, forcommunicating with the capsule-type endoscope; a personal computer,external of the body, that includes a memory for storing image signalsfrom the capsule-type endoscope, an image processing circuit forprocessing image signals and for generating images, and a controlcircuit for controlling the orientation of the capsule-type endoscopeand the timing of spraying the substance; and a display device fordisplaying images processed by the personal computer, said observationmethod comprising the following steps: (a)—specifying a tracking targeton an image that is displayed on the display screen of the displaydevice; (b)—automatically controlling the orientation of thecapsule-type endoscope so that the centerline of an orifice of the sprayunit intersects the tracking target; and (c)—automatically spraying thesubstance when the center axis of the orifice of the spray unitintersects with the tracking target.
 105. An observation method using acapsule-type endoscope system, said system comprising: a capsule-typeendoscope that includes a light source for providing illumination insidea living body, an image pickup unit for capturing images inside thebody, a spray unit for spraying a substance inside the body, and acommunication unit for transmitting image signals taken inside the bodyto outside the body and for receiving signals for controlling the sprayunit from outside the body; an orientation control device, external ofthe body, for controlling the orientation of the capsule-type endoscopewithin the body; a communication device, external of the body, forcommunicating with the capsule-type endoscope; a personal computer,external of the body, that includes a memory for storing image signalsfrom the capsule-type endoscope, an image processing circuit forprocessing image signals and generating images, and a control circuitfor controlling the orientation of the capsule-type endoscope and thetiming of spraying; and a display device for displaying images processedby the personal computer, said observation method comprising thefollowing steps: (a)—analyzing the morphology and color tone of anobject in a captured image and comparing it with particular lesionpatterns stored in the memory of the personal computer; (b)—identifyingthe position of the lesion based on the comparison result of step (a);(c)—automatically specifying the lesion position identified in step (b)for tracking a target; (d)—automatically controlling the orientation ofthe capsule-type endoscope so that a centerline of an orifice of thespray unit intersects with the target; and (e)—automatically sprayingthe substance when the centerline of the orifice intersects with thetarget.
 106. An observation method using a capsule-type endoscopesystem, said system comprising: a capsule-type endoscope that includes alight source for providing illumination inside a living body, an imagepickup unit for capturing images inside the body, a spray unit forspraying a substance inside the body, and a communication unit fortransmitting image signals that are taken within the body to outside thebody and for receiving signals for controlling the spray unit fromoutside the body; a communication device, external of the body, forcommunicating with the capsule-type endoscope; a personal computer,external of the body, that includes a memory for storing image signalsfrom the capsule-type endoscope, an image processing circuit forprocessing image signals and for generating images, and a controlcircuit for controlling the timing of spraying; and a display device fordisplaying images processed by the personal computer; said methodcomprising the following steps: (a)—identifying a lesion by observing animage displayed on the display device; (b)—spraying a substance on thelesion; and (c)—observing the image of the lesion sprayed with thesubstance at a larger magnification than used when observing the imagein step (a).
 107. An observation method using a capsule-type endoscopesystem, said system comprising: a capsule-type endoscope that includes alight source for providing illumination inside a living body, an imagepickup unit for capturing images inside the body, a puncture needle unitfor inserting a needle into tissue so as to inject a substance or tocollect a sample of the tissue, and a communication unit fortransmitting image signals taken within the body to outside the body andfor receiving signals for controlling the puncture needle unit fromoutside the body; a communication device, external of the body, forcommunicating with the capsule-type endoscope; a personal computer,external of the body, that includes a memory for storing image signalsfrom the capsule-type endoscope, an image processing circuit forprocessing image signals and for generating images, and a controlcircuit for controlling the timing of insertion of a puncture needleinto living tissue; and a display device for displaying images processedby the personal computer; said method comprising the following steps:(a)—analyzing the distance the puncture needle has been inserted into aliving tissue after the tip of the puncture needle makes contact with asurface of the living tissue; and (b)—displaying the result of step (a),as well as a captured image, on the display device.
 108. A capsule-typeendoscope for observing an in vivo object, said capsule-type endoscopecomprising: a light source for illuminating the object; an image pickupunit for capturing an image of the object; a transparent cover thatseals the light source and the image pickup unit within a capsule-shapedexternal surface; wherein the image pickup unit comprises an objectiveoptical system and an image pickup element; and the objective opticalsystem satisfies the following two conditions R1≧5 lines per mm R2≧1line per mm where R1 is the resolution on the optical axis at positionsbetween the most object-side surface of the objective optical system andthe point of intersection of the optical axis of the objective opticalsystem with an outer surface of the transparent cover; and R2 is theresolution on the optical axis at positions between the most object-sidesurface of the objective optical system and a far point of the depth offield of the objective optical system.
 109. The capsule-type endoscopeaccording to claim 108, wherein the image pickup unit satisfies thefollowing conditions:80<IH/P<50080<FL/P<500400<Fno/P<3000 where IH is the distance, in mm, between the center andthe furthermost point of the effective image pickup area of thelight-receiving surface of the image pickup element; P is the horizontalpixel pitch, in mm, of the image pickup element; FL is the focal length,in mm, of the objective optical system; and Fno is the effectiveF-number of the objective optical system.
 110. A capsule-type endoscopecomprising: a light source for providing illumination inside a livingbody; an image pickup unit for capturing images inside the body; a sprayunit for spraying a substance inside the body; and a communication unitfor transmitting the image signals to outside the body and for receivingsignals for controlling the spray unit from outside the body; whereinthe spray unit includes a tank that is located inside an exteriorsurface of the capsule-type endoscope and a nozzle that is locatedoutside said exterior surface; and the nozzle is positioned outside afield of view of the objective optical system but where the field ofview of the objective optical system and a spray range of the nozzleoverlap.
 111. A capsule-type endoscope comprising: a light source forproviding illumination inside a living body; an image pickup unit forcapturing images inside the body; a puncture needle unit for inserting aneedle into tissue of the body so as to inject a substance or collect asample of the tissue; and a communication unit for transmitting imagesignals to outside the body and for receiving signals for controllingthe puncture needle unit from outside the body, wherein the image pickupunit includes an objective optical system having a field of view; thepuncture needle unit includes a projection port, a puncture needlestorage space, and a mechanism for pushing the puncture needle throughthe projection port; and the projection port is provided at a locationthat is outside the field of view of the objective optical system but,when the puncture needle is projected through the projection port, a tipof the puncture needle comes within the field of view of the objectiveoptical system before it makes contact with a puncture target region.112. A capsule-type endoscope comprising: a light source for providingillumination inside a living body; an image pickup unit for capturingimages inside the body; a spray unit for spraying a substance inside thebody; and a communication unit for transmitting image signals to outsidethe body and for receiving signals for controlling the spray unit fromoutside the body, wherein the image pickup unit includes an objectiveoptical system having a field of view; the spray unit includes a tankthat is located within an external surface of the capsule-typeendoscope, and a nozzle that is located outside said external surface;and at least a portion of the nozzle is positioned within the field ofview of the objective optical system.
 113. A capsule-type endoscopecomprising: a light source for providing illumination inside a livingbody; an image pickup unit for capturing images inside the body; a sprayunit for spraying a substance inside the body; and a communication unitfor transmitting image signals to outside the body and for receivingsignals for controlling the spray unit from outside the body, wherein:the image pickup unit includes an objective optical system having anoptical axis and a field of view; the spray unit includes a tank locatedwithin an external surface of the capsule-type endoscope and a nozzlethat is located outside said external surface; and the nozzle isoriented so that the following condition is satisfied:15°≦β≦75° where β is the angle between the optical axis of the objectiveoptical system and the centerline of an orifice of the nozzle.
 114. Acapsule-type endoscope comprising: a light source for providingillumination inside a living body; an image pickup unit for capturingimages inside the body; a spray unit for spraying a substance inside thebody using a nozzle; a communication unit for transmitting image signalsto outside the body and for receiving signals for controlling the sprayunit from outside the body; and a transparent cover that seals the lightsource, the image pickup unit, and the communication unit within anexterior surface of the capsule-type endoscope; wherein the image pickupunit includes an objective optical system having a field of view; thespray unit includes a tank that is located inside the exterior surface;and the nozzle is in fluid communication with the tank through thetransparent cover at a location such that the nozzle is outside thefield of view of the objective optical system.
 115. A capsule-typeendoscope comprising: a light source for providing illumination inside aliving body; an image pickup unit for capturing images inside the body;a puncture needle unit for inserting a substance into tissue of the bodyor to collect a sample of the tissue; a communication unit fortransmitting image signals outside the body and for receiving signalsused to control the puncture needle unit from outside the body; and atransparent cover that seals the light source, the image pickup unit,and the communication unit within an external surface of thecapsule-type endoscope; wherein the image pickup unit includes anobjective optical system having a field of view; the puncture needleunit includes a puncture needle projection port, a puncture needlestorage space, and a mechanism for pushing the puncture needle throughthe puncture needle projection port; and the puncture needle projectionport passes through the transparent cover at a location that is outsidethe field of view of the objective optical system.
 116. The capsule-typeendoscope according to claim 110, wherein the spray unit is detachablyattached to the capsule.
 117. The capsule-type endoscope according toclaim 111, wherein the puncture needle unit is detachably attached tothe capsule.
 118. The capsule-type endoscope according to claim 112,wherein the spray unit is detachably attached to the capsule.
 119. Thecapsule-type endoscope according to claim 113, wherein the spray unit isdetachably attached to the capsule.
 120. The capsule-type endoscopeaccording to claim 114, wherein the spray unit is detachably attached tothe capsule.